diff --git a/src/components/views/messages/DownloadActionButton.tsx b/src/components/views/messages/DownloadActionButton.tsx
index 53cdf74b32..d1d416d7e3 100644
--- a/src/components/views/messages/DownloadActionButton.tsx
+++ b/src/components/views/messages/DownloadActionButton.tsx
@@ -63,17 +63,17 @@ export default class DownloadActionButton extends React.PureComponent<IProps, IS
 
         if (this.state.blob) {
             // Cheat and trigger a download, again.
-            return this.doDownload();
+            return this.doDownload(this.state.blob);
         }
 
         const blob = await this.props.mediaEventHelperGet().sourceBlob.value;
         this.setState({ blob });
-        await this.doDownload();
+        await this.doDownload(blob);
     };
 
-    private async doDownload(): Promise<void> {
+    private async doDownload(blob: Blob): Promise<void> {
         await this.downloader.download({
-            blob: this.state.blob,
+            blob,
             name: this.props.mediaEventHelperGet().fileName,
         });
         this.setState({ loading: false });
diff --git a/src/components/views/messages/EditHistoryMessage.tsx b/src/components/views/messages/EditHistoryMessage.tsx
index 312e694786..ca8a8599fd 100644
--- a/src/components/views/messages/EditHistoryMessage.tsx
+++ b/src/components/views/messages/EditHistoryMessage.tsx
@@ -79,7 +79,7 @@ export default class EditHistoryMessage extends React.PureComponent<IProps, ISta
             ConfirmAndWaitRedactDialog,
             {
                 redact: async () => {
-                    await cli.redactEvent(event.getRoomId(), event.getId());
+                    await cli.redactEvent(event.getRoomId()!, event.getId());
                 },
             },
             "mx_Dialog_confirmredact",
diff --git a/src/components/views/messages/MAudioBody.tsx b/src/components/views/messages/MAudioBody.tsx
index 082ec4b0bf..86736d4e48 100644
--- a/src/components/views/messages/MAudioBody.tsx
+++ b/src/components/views/messages/MAudioBody.tsx
@@ -76,7 +76,7 @@ export default class MAudioBody extends React.PureComponent<IBodyProps, IState>
         this.setState({ playback });
 
         if (isVoiceMessage(this.props.mxEvent)) {
-            PlaybackQueue.forRoom(this.props.mxEvent.getRoomId()).unsortedEnqueue(this.props.mxEvent, playback);
+            PlaybackQueue.forRoom(this.props.mxEvent.getRoomId()!).unsortedEnqueue(this.props.mxEvent, playback);
         }
 
         // Note: the components later on will handle preparing the Playback class for us.
diff --git a/src/components/views/messages/MBeaconBody.tsx b/src/components/views/messages/MBeaconBody.tsx
index a3d680cb07..25327df74e 100644
--- a/src/components/views/messages/MBeaconBody.tsx
+++ b/src/components/views/messages/MBeaconBody.tsx
@@ -22,6 +22,7 @@ import {
     MatrixEventEvent,
     MatrixClient,
     RelationType,
+    IRedactOpts,
 } from "matrix-js-sdk/src/matrix";
 import { BeaconLocationState } from "matrix-js-sdk/src/content-helpers";
 import { randomString } from "matrix-js-sdk/src/randomstring";
@@ -107,15 +108,15 @@ const useHandleBeaconRedaction = (
     const onBeforeBeaconInfoRedaction = useCallback(
         (_event: MatrixEvent, redactionEvent: MatrixEvent) => {
             const relations = getRelationsForEvent
-                ? getRelationsForEvent(event.getId(), RelationType.Reference, M_BEACON.name)
+                ? getRelationsForEvent(event.getId()!, RelationType.Reference, M_BEACON.name)
                 : undefined;
 
             relations?.getRelations()?.forEach((locationEvent) => {
                 matrixClient.redactEvent(
-                    locationEvent.getRoomId(),
-                    locationEvent.getId(),
+                    locationEvent.getRoomId()!,
+                    locationEvent.getId()!,
                     undefined,
-                    redactionEvent.getContent(),
+                    redactionEvent.getContent<IRedactOpts>(),
                 );
             });
         },
@@ -132,7 +133,7 @@ const useHandleBeaconRedaction = (
 
 const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelationsForEvent }, ref) => {
     const { beacon, isLive, latestLocationState, waitingToStart } = useBeaconState(mxEvent);
-    const mapId = useUniqueId(mxEvent.getId());
+    const mapId = useUniqueId(mxEvent.getId()!);
 
     const matrixClient = useContext(MatrixClientContext);
     const [error, setError] = useState<Error>();
@@ -159,7 +160,7 @@ const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelati
         Modal.createDialog(
             BeaconViewDialog,
             {
-                roomId: mxEvent.getRoomId(),
+                roomId: mxEvent.getRoomId()!,
                 matrixClient,
                 initialFocusedBeacon: beacon,
             },
@@ -170,11 +171,11 @@ const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelati
     };
 
     let map: JSX.Element;
-    if (displayStatus === BeaconDisplayStatus.Active && !isMapDisplayError) {
+    if (displayStatus === BeaconDisplayStatus.Active && !isMapDisplayError && latestLocationState?.uri) {
         map = (
             <Map
                 id={mapId}
-                centerGeoUri={latestLocationState?.uri}
+                centerGeoUri={latestLocationState.uri}
                 onError={setError}
                 onClick={onClick}
                 className="mx_MBeaconBody_map"
@@ -183,7 +184,7 @@ const MBeaconBody: React.FC<IBodyProps> = React.forwardRef(({ mxEvent, getRelati
                     <SmartMarker
                         map={map}
                         id={`${mapId}-marker`}
-                        geoUri={latestLocationState?.uri}
+                        geoUri={latestLocationState.uri!}
                         roomMember={markerRoomMember ?? undefined}
                         useMemberColor
                     />
diff --git a/src/components/views/messages/MFileBody.tsx b/src/components/views/messages/MFileBody.tsx
index df97bdad83..ae7a8d881d 100644
--- a/src/components/views/messages/MFileBody.tsx
+++ b/src/components/views/messages/MFileBody.tsx
@@ -78,7 +78,7 @@ cacheDownloadIcon();
  * @param {HTMLElement} element The element to get the current style of.
  * @return {string} The CSS style encoded as a string.
  */
-export function computedStyle(element: HTMLElement): string {
+export function computedStyle(element: HTMLElement | null): string {
     if (!element) {
         return "";
     }
@@ -142,6 +142,7 @@ export default class MFileBody extends React.Component<IProps, IState> {
     }
 
     private downloadFile(fileName: string, text: string): void {
+        if (!this.state.decryptedBlob) return;
         this.fileDownloader.download({
             blob: this.state.decryptedBlob,
             name: fileName,
diff --git a/src/components/views/messages/MImageBody.tsx b/src/components/views/messages/MImageBody.tsx
index f556b59cf7..ad99aa142e 100644
--- a/src/components/views/messages/MImageBody.tsx
+++ b/src/components/views/messages/MImageBody.tsx
@@ -104,9 +104,10 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
 
             const content = this.props.mxEvent.getContent<IMediaEventContent>();
             const httpUrl = this.state.contentUrl;
+            if (!httpUrl) return;
             const params: Omit<ComponentProps<typeof ImageView>, "onFinished"> = {
                 src: httpUrl,
-                name: content.body?.length > 0 ? content.body : _t("Attachment"),
+                name: content.body && content.body.length > 0 ? content.body : _t("Attachment"),
                 mxEvent: this.props.mxEvent,
                 permalinkCreator: this.props.permalinkCreator,
             };
@@ -135,7 +136,12 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
     protected onImageEnter = (e: React.MouseEvent<HTMLImageElement>): void => {
         this.setState({ hover: true });
 
-        if (!this.state.showImage || !this.state.isAnimated || SettingsStore.getValue("autoplayGifs")) {
+        if (
+            !this.state.contentUrl ||
+            !this.state.showImage ||
+            !this.state.isAnimated ||
+            SettingsStore.getValue("autoplayGifs")
+        ) {
             return;
         }
         const imgElement = e.currentTarget;
@@ -145,11 +151,12 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
     protected onImageLeave = (e: React.MouseEvent<HTMLImageElement>): void => {
         this.setState({ hover: false });
 
-        if (!this.state.showImage || !this.state.isAnimated || SettingsStore.getValue("autoplayGifs")) {
+        const url = this.state.thumbUrl ?? this.state.contentUrl;
+        if (!url || !this.state.showImage || !this.state.isAnimated || SettingsStore.getValue("autoplayGifs")) {
             return;
         }
         const imgElement = e.currentTarget;
-        imgElement.src = this.state.thumbUrl ?? this.state.contentUrl;
+        imgElement.src = url;
     };
 
     private clearError = (): void => {
@@ -285,7 +292,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
                     img.onerror = reject;
                 });
                 img.crossOrigin = "Anonymous"; // CORS allow canvas access
-                img.src = contentUrl;
+                img.src = contentUrl ?? "";
 
                 try {
                     await loadPromise;
@@ -379,7 +386,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
 
     protected messageContent(
         contentUrl: string,
-        thumbUrl: string,
+        thumbUrl: string | null,
         content: IMediaEventContent,
         forcedHeight?: number,
     ): JSX.Element {
@@ -579,7 +586,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
         }
 
         let contentUrl = this.state.contentUrl;
-        let thumbUrl: string | undefined;
+        let thumbUrl: string | null;
         if (this.props.forExport) {
             contentUrl = this.props.mxEvent.getContent().url ?? this.props.mxEvent.getContent().file?.url;
             thumbUrl = contentUrl;
@@ -589,7 +596,7 @@ export default class MImageBody extends React.Component<IBodyProps, IState> {
             thumbUrl = this.state.thumbUrl ?? this.state.contentUrl;
         }
 
-        const thumbnail = this.messageContent(contentUrl, thumbUrl, content);
+        const thumbnail = contentUrl ? this.messageContent(contentUrl, thumbUrl, content) : undefined;
         const fileBody = this.getFileBody();
 
         return (
diff --git a/src/components/views/messages/MImageReplyBody.tsx b/src/components/views/messages/MImageReplyBody.tsx
index 13a07c162a..68a39d23d6 100644
--- a/src/components/views/messages/MImageReplyBody.tsx
+++ b/src/components/views/messages/MImageReplyBody.tsx
@@ -36,7 +36,9 @@ export default class MImageReplyBody extends MImageBody {
         }
 
         const content = this.props.mxEvent.getContent<IMediaEventContent>();
-        const thumbnail = this.messageContent(this.state.contentUrl, this.state.thumbUrl, content, FORCED_IMAGE_HEIGHT);
+        const thumbnail = this.state.contentUrl
+            ? this.messageContent(this.state.contentUrl, this.state.thumbUrl, content, FORCED_IMAGE_HEIGHT)
+            : undefined;
 
         return <div className="mx_MImageReplyBody">{thumbnail}</div>;
     }
diff --git a/src/components/views/messages/MJitsiWidgetEvent.tsx b/src/components/views/messages/MJitsiWidgetEvent.tsx
index 50b180beed..b299d96f6d 100644
--- a/src/components/views/messages/MJitsiWidgetEvent.tsx
+++ b/src/components/views/messages/MJitsiWidgetEvent.tsx
@@ -38,6 +38,7 @@ export default class MJitsiWidgetEvent extends React.PureComponent<IProps> {
         const prevUrl = this.props.mxEvent.getPrevContent()["url"];
         const senderName = this.props.mxEvent.sender?.name || this.props.mxEvent.getSender();
         const room = MatrixClientPeg.get().getRoom(this.props.mxEvent.getRoomId());
+        if (!room) return null;
         const widgetId = this.props.mxEvent.getStateKey();
         const widget = WidgetStore.instance.getRoom(room.roomId, true).widgets.find((w) => w.id === widgetId);
 
diff --git a/src/components/views/messages/MKeyVerificationConclusion.tsx b/src/components/views/messages/MKeyVerificationConclusion.tsx
index 24b925544e..fc354bd973 100644
--- a/src/components/views/messages/MKeyVerificationConclusion.tsx
+++ b/src/components/views/messages/MKeyVerificationConclusion.tsx
@@ -114,16 +114,16 @@ export default class MKeyVerificationConclusion extends React.Component<IProps>
 
         if (request.done) {
             title = _t("You verified %(name)s", {
-                name: getNameForEventRoom(request.otherUserId, mxEvent.getRoomId()),
+                name: getNameForEventRoom(request.otherUserId, mxEvent.getRoomId()!),
             });
         } else if (request.cancelled) {
             const userId = request.cancellingUserId;
             if (userId === myUserId) {
                 title = _t("You cancelled verifying %(name)s", {
-                    name: getNameForEventRoom(request.otherUserId, mxEvent.getRoomId()),
+                    name: getNameForEventRoom(request.otherUserId, mxEvent.getRoomId()!),
                 });
-            } else {
-                title = _t("%(name)s cancelled verifying", { name: getNameForEventRoom(userId, mxEvent.getRoomId()) });
+            } else if (userId) {
+                title = _t("%(name)s cancelled verifying", { name: getNameForEventRoom(userId, mxEvent.getRoomId()!) });
             }
         }
 
@@ -135,7 +135,7 @@ export default class MKeyVerificationConclusion extends React.Component<IProps>
                 <EventTileBubble
                     className={classes}
                     title={title}
-                    subtitle={userLabelForEventRoom(request.otherUserId, mxEvent.getRoomId())}
+                    subtitle={userLabelForEventRoom(request.otherUserId, mxEvent.getRoomId()!)}
                     timestamp={this.props.timestamp}
                 />
             );
diff --git a/src/components/views/messages/MKeyVerificationRequest.tsx b/src/components/views/messages/MKeyVerificationRequest.tsx
index 8647a824ec..13bb4405ac 100644
--- a/src/components/views/messages/MKeyVerificationRequest.tsx
+++ b/src/components/views/messages/MKeyVerificationRequest.tsx
@@ -15,7 +15,7 @@ limitations under the License.
 */
 
 import React from "react";
-import { MatrixEvent } from "matrix-js-sdk/src/matrix";
+import { MatrixEvent, User } from "matrix-js-sdk/src/matrix";
 import { logger } from "matrix-js-sdk/src/logger";
 import { VerificationRequestEvent } from "matrix-js-sdk/src/crypto/verification/request/VerificationRequest";
 
@@ -48,8 +48,11 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
     }
 
     private openRequest = (): void => {
+        let member: User | undefined;
         const { verificationRequest } = this.props.mxEvent;
-        const member = MatrixClientPeg.get().getUser(verificationRequest.otherUserId);
+        if (verificationRequest) {
+            member = MatrixClientPeg.get().getUser(verificationRequest.otherUserId) ?? undefined;
+        }
         RightPanelStore.instance.setCards([
             { phase: RightPanelPhases.RoomSummary },
             { phase: RightPanelPhases.RoomMemberInfo, state: { member } },
@@ -90,14 +93,14 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
         if (userId === myUserId) {
             return _t("You accepted");
         } else {
-            return _t("%(name)s accepted", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()) });
+            return _t("%(name)s accepted", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()!) });
         }
     }
 
     private cancelledLabel(userId: string): string {
         const client = MatrixClientPeg.get();
         const myUserId = client.getUserId();
-        const { cancellationCode } = this.props.mxEvent.verificationRequest;
+        const cancellationCode = this.props.mxEvent.verificationRequest?.cancellationCode;
         const declined = cancellationCode === "m.user";
         if (userId === myUserId) {
             if (declined) {
@@ -107,9 +110,9 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
             }
         } else {
             if (declined) {
-                return _t("%(name)s declined", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()) });
+                return _t("%(name)s declined", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()!) });
             } else {
-                return _t("%(name)s cancelled", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()) });
+                return _t("%(name)s cancelled", { name: getNameForEventRoom(userId, this.props.mxEvent.getRoomId()!) });
             }
         }
     }
@@ -136,7 +139,7 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
                     </AccessibleButton>
                 );
             } else if (request.cancelled) {
-                stateLabel = this.cancelledLabel(request.cancellingUserId);
+                stateLabel = this.cancelledLabel(request.cancellingUserId!);
             } else if (request.accepting) {
                 stateLabel = _t("Accepting…");
             } else if (request.declining) {
@@ -146,9 +149,9 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
         }
 
         if (!request.initiatedByMe) {
-            const name = getNameForEventRoom(request.requestingUserId, mxEvent.getRoomId());
+            const name = getNameForEventRoom(request.requestingUserId, mxEvent.getRoomId()!);
             title = _t("%(name)s wants to verify", { name });
-            subtitle = userLabelForEventRoom(request.requestingUserId, mxEvent.getRoomId());
+            subtitle = userLabelForEventRoom(request.requestingUserId, mxEvent.getRoomId()!);
             if (request.canAccept) {
                 stateNode = (
                     <div className="mx_cryptoEvent_buttons">
@@ -164,7 +167,7 @@ export default class MKeyVerificationRequest extends React.Component<IProps> {
         } else {
             // request sent by us
             title = _t("You sent a verification request");
-            subtitle = userLabelForEventRoom(request.receivingUserId, mxEvent.getRoomId());
+            subtitle = userLabelForEventRoom(request.receivingUserId, mxEvent.getRoomId()!);
         }
 
         if (title) {
diff --git a/src/components/views/messages/MPollBody.tsx b/src/components/views/messages/MPollBody.tsx
index e65a8f67e6..21c3ee7ec1 100644
--- a/src/components/views/messages/MPollBody.tsx
+++ b/src/components/views/messages/MPollBody.tsx
@@ -118,16 +118,17 @@ export function pollAlreadyHasVotes(mxEvent: MatrixEvent, getRelationsForEvent?:
 }
 
 export function launchPollEditor(mxEvent: MatrixEvent, getRelationsForEvent?: GetRelationsForEvent): void {
+    const room = MatrixClientPeg.get().getRoom(mxEvent.getRoomId());
     if (pollAlreadyHasVotes(mxEvent, getRelationsForEvent)) {
         Modal.createDialog(ErrorDialog, {
             title: _t("Can't edit poll"),
             description: _t("Sorry, you can't edit a poll after votes have been cast."),
         });
-    } else {
+    } else if (room) {
         Modal.createDialog(
             PollCreateDialog,
             {
-                room: MatrixClientPeg.get().getRoom(mxEvent.getRoomId()),
+                room,
                 threadId: mxEvent.getThread()?.id,
                 editingMxEvent: mxEvent,
             },
diff --git a/src/components/views/messages/MVideoBody.tsx b/src/components/views/messages/MVideoBody.tsx
index a7e60dfd5a..6be311e868 100644
--- a/src/components/views/messages/MVideoBody.tsx
+++ b/src/components/views/messages/MVideoBody.tsx
@@ -111,7 +111,7 @@ export default class MVideoBody extends React.PureComponent<IBodyProps, IState>
         canvas.height = height;
 
         const pixels = decode(info[BLURHASH_FIELD], width, height);
-        const ctx = canvas.getContext("2d");
+        const ctx = canvas.getContext("2d")!;
         const imgData = ctx.createImageData(width, height);
         imgData.data.set(pixels);
         ctx.putImageData(imgData, 0, 0);
@@ -128,7 +128,7 @@ export default class MVideoBody extends React.PureComponent<IBodyProps, IState>
             image.onload = () => {
                 this.setState({ posterLoading: false });
             };
-            image.src = media.thumbnailHttp;
+            image.src = media.thumbnailHttp!;
         }
     }
 
diff --git a/src/components/views/messages/MessageEvent.tsx b/src/components/views/messages/MessageEvent.tsx
index 7e2a8b8db9..65b7133b51 100644
--- a/src/components/views/messages/MessageEvent.tsx
+++ b/src/components/views/messages/MessageEvent.tsx
@@ -185,9 +185,9 @@ export default class MessageEvent extends React.Component<IProps> implements IMe
             const allowRender = localStorage.getItem(key) === "true";
 
             if (!allowRender) {
-                const userDomain = this.props.mxEvent.getSender().split(":").slice(1).join(":");
-                const userBanned = Mjolnir.sharedInstance().isUserBanned(this.props.mxEvent.getSender());
-                const serverBanned = Mjolnir.sharedInstance().isServerBanned(userDomain);
+                const userDomain = this.props.mxEvent.getSender()?.split(":").slice(1).join(":");
+                const userBanned = Mjolnir.sharedInstance().isUserBanned(this.props.mxEvent.getSender()!);
+                const serverBanned = userDomain && Mjolnir.sharedInstance().isServerBanned(userDomain);
 
                 if (userBanned || serverBanned) {
                     BodyType = MjolnirBody;
diff --git a/src/components/views/messages/ReactionsRow.tsx b/src/components/views/messages/ReactionsRow.tsx
index 6d7b0b2d17..bde1cba43c 100644
--- a/src/components/views/messages/ReactionsRow.tsx
+++ b/src/components/views/messages/ReactionsRow.tsx
@@ -34,8 +34,8 @@ const MAX_ITEMS_WHEN_LIMITED = 8;
 const ReactButton: React.FC<IProps> = ({ mxEvent, reactions }) => {
     const [menuDisplayed, button, openMenu, closeMenu] = useContextMenu();
 
-    let contextMenu;
-    if (menuDisplayed) {
+    let contextMenu: JSX.Element | undefined;
+    if (menuDisplayed && button.current) {
         const buttonRect = button.current.getBoundingClientRect();
         contextMenu = (
             <ContextMenu {...aboveLeftOf(buttonRect)} onFinished={closeMenu} managed={false}>
@@ -73,7 +73,7 @@ interface IProps {
 }
 
 interface IState {
-    myReactions: MatrixEvent[];
+    myReactions: MatrixEvent[] | null;
     showAll: boolean;
 }
 
@@ -147,8 +147,9 @@ export default class ReactionsRow extends React.PureComponent<IProps, IState> {
         if (!reactions) {
             return null;
         }
-        const userId = this.context.room.client.getUserId();
-        const myReactions = reactions.getAnnotationsBySender()[userId];
+        const userId = this.context.room?.client.getUserId();
+        if (!userId) return null;
+        const myReactions = reactions.getAnnotationsBySender()?.[userId];
         if (!myReactions) {
             return null;
         }
@@ -171,19 +172,17 @@ export default class ReactionsRow extends React.PureComponent<IProps, IState> {
 
         let items = reactions
             .getSortedAnnotationsByKey()
-            .map(([content, events]) => {
+            ?.map(([content, events]) => {
                 const count = events.size;
                 if (!count) {
                     return null;
                 }
-                const myReactionEvent =
-                    myReactions &&
-                    myReactions.find((mxEvent) => {
-                        if (mxEvent.isRedacted()) {
-                            return false;
-                        }
-                        return mxEvent.getRelation().key === content;
-                    });
+                const myReactionEvent = myReactions?.find((mxEvent) => {
+                    if (mxEvent.isRedacted()) {
+                        return false;
+                    }
+                    return mxEvent.getRelation()?.key === content;
+                });
                 return (
                     <ReactionsRowButton
                         key={content}
@@ -201,7 +200,7 @@ export default class ReactionsRow extends React.PureComponent<IProps, IState> {
             })
             .filter((item) => !!item);
 
-        if (!items.length) return null;
+        if (!items?.length) return null;
 
         // Show the first MAX_ITEMS if there are MAX_ITEMS + 1 or more items.
         // The "+ 1" ensure that the "show all" reveals something that takes up
@@ -216,7 +215,7 @@ export default class ReactionsRow extends React.PureComponent<IProps, IState> {
             );
         }
 
-        let addReactionButton: JSX.Element;
+        let addReactionButton: JSX.Element | undefined;
         if (this.context.canReact) {
             addReactionButton = <ReactButton mxEvent={mxEvent} reactions={reactions} />;
         }
diff --git a/src/components/views/messages/ReactionsRowButton.tsx b/src/components/views/messages/ReactionsRowButton.tsx
index 60bad283b7..284b713821 100644
--- a/src/components/views/messages/ReactionsRowButton.tsx
+++ b/src/components/views/messages/ReactionsRowButton.tsx
@@ -24,7 +24,6 @@ import dis from "../../../dispatcher/dispatcher";
 import ReactionsRowButtonTooltip from "./ReactionsRowButtonTooltip";
 import AccessibleButton from "../elements/AccessibleButton";
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
-
 interface IProps {
     // The event we're displaying reactions for
     mxEvent: MatrixEvent;
@@ -57,9 +56,9 @@ export default class ReactionsRowButton extends React.PureComponent<IProps, ISta
     public onClick = (): void => {
         const { mxEvent, myReactionEvent, content } = this.props;
         if (myReactionEvent) {
-            this.context.redactEvent(mxEvent.getRoomId(), myReactionEvent.getId());
+            this.context.redactEvent(mxEvent.getRoomId()!, myReactionEvent.getId());
         } else {
-            this.context.sendEvent(mxEvent.getRoomId(), "m.reaction", {
+            this.context.sendEvent(mxEvent.getRoomId()!, "m.reaction", {
                 "m.relates_to": {
                     rel_type: "m.annotation",
                     event_id: mxEvent.getId(),
@@ -110,8 +109,8 @@ export default class ReactionsRowButton extends React.PureComponent<IProps, ISta
         if (room) {
             const senders: string[] = [];
             for (const reactionEvent of reactionEvents) {
-                const member = room.getMember(reactionEvent.getSender());
-                senders.push(member?.name || reactionEvent.getSender());
+                const member = room.getMember(reactionEvent.getSender()!);
+                senders.push(member?.name || reactionEvent.getSender()!);
             }
 
             const reactors = formatCommaSeparatedList(senders, 6);
diff --git a/src/components/views/messages/ReactionsRowButtonTooltip.tsx b/src/components/views/messages/ReactionsRowButtonTooltip.tsx
index 3ed211be32..c665f60620 100644
--- a/src/components/views/messages/ReactionsRowButtonTooltip.tsx
+++ b/src/components/views/messages/ReactionsRowButtonTooltip.tsx
@@ -22,7 +22,6 @@ import { _t } from "../../../languageHandler";
 import { formatCommaSeparatedList } from "../../../utils/FormattingUtils";
 import Tooltip from "../elements/Tooltip";
 import MatrixClientContext from "../../../contexts/MatrixClientContext";
-
 interface IProps {
     // The event we're displaying reactions for
     mxEvent: MatrixEvent;
@@ -45,8 +44,8 @@ export default class ReactionsRowButtonTooltip extends React.PureComponent<IProp
         if (room) {
             const senders: string[] = [];
             for (const reactionEvent of reactionEvents) {
-                const member = room.getMember(reactionEvent.getSender());
-                const name = member ? member.name : reactionEvent.getSender();
+                const member = room.getMember(reactionEvent.getSender()!);
+                const name = member?.name ?? reactionEvent.getSender()!;
                 senders.push(name);
             }
             const shortName = unicodeToShortcode(content);
diff --git a/src/components/views/messages/RedactedBody.tsx b/src/components/views/messages/RedactedBody.tsx
index 9c36a1bb38..7b8ddf07a4 100644
--- a/src/components/views/messages/RedactedBody.tsx
+++ b/src/components/views/messages/RedactedBody.tsx
@@ -23,7 +23,6 @@ import MatrixClientContext from "../../../contexts/MatrixClientContext";
 import { formatFullDate } from "../../../DateUtils";
 import SettingsStore from "../../../settings/SettingsStore";
 import { IBodyProps } from "./IBodyProps";
-
 interface IProps {
     mxEvent: MatrixEvent;
 }
@@ -40,8 +39,10 @@ const RedactedBody = React.forwardRef<any, IProps | IBodyProps>(({ mxEvent }, re
     }
 
     const showTwelveHour = SettingsStore.getValue("showTwelveHourTimestamps");
-    const fullDate = formatFullDate(new Date(unsigned.redacted_because.origin_server_ts), showTwelveHour);
-    const titleText = _t("Message deleted on %(date)s", { date: fullDate });
+    const fullDate = unsigned.redacted_because
+        ? formatFullDate(new Date(unsigned.redacted_because.origin_server_ts), showTwelveHour)
+        : undefined;
+    const titleText = fullDate ? _t("Message deleted on %(date)s", { date: fullDate }) : undefined;
 
     return (
         <span className="mx_RedactedBody" ref={ref} title={titleText}>
diff --git a/src/components/views/messages/RoomAvatarEvent.tsx b/src/components/views/messages/RoomAvatarEvent.tsx
index 84fd4660bf..15e535210a 100644
--- a/src/components/views/messages/RoomAvatarEvent.tsx
+++ b/src/components/views/messages/RoomAvatarEvent.tsx
@@ -26,7 +26,6 @@ import AccessibleButton from "../elements/AccessibleButton";
 import { mediaFromMxc } from "../../../customisations/Media";
 import RoomAvatar from "../avatars/RoomAvatar";
 import ImageView from "../elements/ImageView";
-
 interface IProps {
     /* the MatrixEvent to show */
     mxEvent: MatrixEvent;
@@ -37,6 +36,7 @@ export default class RoomAvatarEvent extends React.Component<IProps> {
         const cli = MatrixClientPeg.get();
         const ev = this.props.mxEvent;
         const httpUrl = mediaFromMxc(ev.getContent().url).srcHttp;
+        if (!httpUrl) return;
 
         const room = cli.getRoom(this.props.mxEvent.getRoomId());
         const text = _t("%(senderDisplayName)s changed the avatar for %(roomName)s", {
@@ -48,7 +48,7 @@ export default class RoomAvatarEvent extends React.Component<IProps> {
             src: httpUrl,
             name: text,
         };
-        Modal.createDialog(ImageView, params, "mx_Dialog_lightbox", null, true);
+        Modal.createDialog(ImageView, params, "mx_Dialog_lightbox", undefined, true);
     };
 
     public render(): React.ReactNode {
diff --git a/src/components/views/messages/TextualBody.tsx b/src/components/views/messages/TextualBody.tsx
index 05f6da046d..488c699aed 100644
--- a/src/components/views/messages/TextualBody.tsx
+++ b/src/components/views/messages/TextualBody.tsx
@@ -34,7 +34,6 @@ import { isPermalinkHost, tryTransformPermalinkToLocalHref } from "../../../util
 import { copyPlaintext } from "../../../utils/strings";
 import AccessibleTooltipButton from "../elements/AccessibleTooltipButton";
 import UIStore from "../../../stores/UIStore";
-import { ComposerInsertPayload } from "../../../dispatcher/payloads/ComposerInsertPayload";
 import { Action } from "../../../dispatcher/actions";
 import GenericTextContextMenu from "../context_menus/GenericTextContextMenu";
 import Spoiler from "../elements/Spoiler";
@@ -109,7 +108,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
                 for (let i = 0; i < pres.length; i++) {
                     // If there already is a div wrapping the codeblock we want to skip this.
                     // This happens after the codeblock was edited.
-                    if (pres[i].parentElement.className == "mx_EventTile_pre_container") continue;
+                    if (pres[i].parentElement?.className == "mx_EventTile_pre_container") continue;
                     // Add code element if it's missing since we depend on it
                     if (pres[i].getElementsByTagName("code").length == 0) {
                         this.addCodeElement(pres[i]);
@@ -189,8 +188,8 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
         if (expansionButtonExists.length > 0) button.className += "mx_EventTile_buttonBottom";
 
         button.onclick = async (): Promise<void> => {
-            const copyCode = button.parentElement.getElementsByTagName("code")[0];
-            const successful = await copyPlaintext(copyCode.textContent);
+            const copyCode = button.parentElement?.getElementsByTagName("code")[0];
+            const successful = copyCode?.textContent ? await copyPlaintext(copyCode.textContent) : false;
 
             const buttonRect = button.getBoundingClientRect();
             const { close } = ContextMenu.createMenu(GenericTextContextMenu, {
@@ -209,7 +208,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
         div.className = "mx_EventTile_pre_container";
 
         // Insert containing div in place of <pre> block
-        pre.parentNode.replaceChild(div, pre);
+        pre.parentNode?.replaceChild(div, pre);
         // Append <pre> block and copy button to container
         div.appendChild(pre);
 
@@ -238,7 +237,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
     }
 
     private highlightCode(code: HTMLElement): void {
-        if (code.textContent.length > MAX_HIGHLIGHT_LENGTH) {
+        if (code.textContent && code.textContent.length > MAX_HIGHLIGHT_LENGTH) {
             console.log(
                 "Code block is bigger than highlight limit (" +
                     code.textContent.length +
@@ -265,7 +264,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
             // We don't use highlightElement here because we can't force language detection
             // off. It should use the one we've found in the CSS class but we'd rather pass
             // it in explicitly to make sure.
-            code.innerHTML = highlight.highlight(code.textContent, { language: advertisedLang }).value;
+            code.innerHTML = highlight.highlight(code.textContent ?? "", { language: advertisedLang }).value;
         } else if (
             SettingsStore.getValue("enableSyntaxHighlightLanguageDetection") &&
             code.parentElement instanceof HTMLPreElement
@@ -277,7 +276,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
             // work on the DOM with highlightElement because that also adds CSS
             // classes to the pre/code element that we don't want (the CSS
             // conflicts with our own).
-            code.innerHTML = highlight.highlightAuto(code.textContent).value;
+            code.innerHTML = highlight.highlightAuto(code.textContent ?? "").value;
         }
     }
 
@@ -317,7 +316,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
     private calculateUrlPreview(): void {
         //console.info("calculateUrlPreview: ShowUrlPreview for %s is %s", this.props.mxEvent.getId(), this.props.showUrlPreview);
 
-        if (this.props.showUrlPreview) {
+        if (this.props.showUrlPreview && this.contentRef.current) {
             // pass only the first child which is the event tile otherwise this recurses on edited events
             let links = this.findLinks([this.contentRef.current]);
             if (links.length) {
@@ -347,7 +346,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
                 const spoiler = <Spoiler reason={reason} contentHtml={node.outerHTML} />;
 
                 ReactDOM.render(spoiler, spoilerContainer);
-                node.parentNode.replaceChild(spoilerContainer, node);
+                node.parentNode?.replaceChild(spoilerContainer, node);
 
                 node = spoilerContainer;
             }
@@ -395,12 +394,12 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
         }
 
         const url = node.getAttribute("href");
-        const host = url.match(/^https?:\/\/(.*?)(\/|$)/)[1];
+        const host = url?.match(/^https?:\/\/(.*?)(\/|$)/)?.[1];
 
         // never preview permalinks (if anything we should give a smart
         // preview of the room/user they point to: nobody needs to be reminded
         // what the matrix.to site looks like).
-        if (isPermalinkHost(host)) return false;
+        if (!host || isPermalinkHost(host)) return false;
 
         if (node.textContent?.toLowerCase().trim().startsWith(host.toLowerCase())) {
             // it's a "foo.pl" style link
@@ -422,7 +421,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
 
     private onEmoteSenderClick = (): void => {
         const mxEvent = this.props.mxEvent;
-        dis.dispatch<ComposerInsertPayload>({
+        dis.dispatch({
             action: Action.ComposerInsert,
             userId: mxEvent.getSender(),
             timelineRenderingType: this.context.timelineRenderingType,
@@ -482,10 +481,10 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
 
         // Go fetch a scalar token
         const integrationManager = managers.getPrimaryManager();
-        const scalarClient = integrationManager.getScalarClient();
-        scalarClient.connect().then(() => {
+        const scalarClient = integrationManager?.getScalarClient();
+        scalarClient?.connect().then(() => {
             const completeUrl = scalarClient.getStarterLink(starterLink);
-            const integrationsUrl = integrationManager.uiUrl;
+            const integrationsUrl = integrationManager!.uiUrl;
             Modal.createDialog(QuestionDialog, {
                 title: _t("Add an Integration"),
                 description: (
@@ -508,7 +507,7 @@ export default class TextualBody extends React.Component<IBodyProps, IState> {
                     const left = (window.screen.width - width) / 2;
                     const top = (window.screen.height - height) / 2;
                     const features = `height=${height}, width=${width}, top=${top}, left=${left},`;
-                    const wnd = window.open(completeUrl, "_blank", features);
+                    const wnd = window.open(completeUrl, "_blank", features)!;
                     wnd.opener = null;
                 },
             });
diff --git a/src/settings/enums/ImageSize.ts b/src/settings/enums/ImageSize.ts
index 28f72cb8de..6c05497794 100644
--- a/src/settings/enums/ImageSize.ts
+++ b/src/settings/enums/ImageSize.ts
@@ -35,7 +35,7 @@ export enum ImageSize {
  * @param {number} maxHeight Overrides the default height limit
  * @returns {Dimensions} The suggested maximum dimensions for the image
  */
-export function suggestedSize(size: ImageSize, contentSize: Dimensions, maxHeight?: number): Dimensions {
+export function suggestedSize(size: ImageSize, contentSize: Dimensions, maxHeight?: number): Required<Dimensions> {
     const aspectRatio = contentSize.w! / contentSize.h!;
     const portrait = aspectRatio < 1;
 
diff --git a/src/utils/FileDownloader.ts b/src/utils/FileDownloader.ts
index 3ed848e455..a2c89d0228 100644
--- a/src/utils/FileDownloader.ts
+++ b/src/utils/FileDownloader.ts
@@ -14,7 +14,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-export type getIframeFn = () => HTMLIFrameElement; // eslint-disable-line @typescript-eslint/naming-convention
+export type GetIframeFn = () => HTMLIFrameElement | null;
 
 export const DEFAULT_STYLES = {
     imgSrc: "",
@@ -75,7 +75,7 @@ export class FileDownloader {
      * @param iframeFn Function to get a pre-configured iframe. Set to null to have the downloader
      * use a generic, hidden, iframe.
      */
-    public constructor(private iframeFn?: getIframeFn) {}
+    public constructor(private iframeFn?: GetIframeFn) {}
 
     private get iframe(): HTMLIFrameElement {
         const iframe = this.iframeFn?.();