diff --git a/src/components/LeftSidebar/LeftSidebar.vue b/src/components/LeftSidebar/LeftSidebar.vue
index 469571312d2..94def556e4e 100644
--- a/src/components/LeftSidebar/LeftSidebar.vue
+++ b/src/components/LeftSidebar/LeftSidebar.vue
@@ -341,7 +341,7 @@
 					class="scroller"
 					@scroll="debounceHandleScroll" />
 				<NcButton
-					v-if="!showThreadsList && !preventFindingUnread && lastUnreadMentionBelowViewportIndex !== null && !filters.includes('mentions')"
+					v-if="!showThreadsList && lastUnreadMentionBelowViewportIndex !== null && !filters.includes('mentions')"
 					class="unread-mention-button"
 					variant="primary"
 					@click="scrollBottomUnread">
@@ -633,7 +633,6 @@ export default {
 			 * @type {number|null}
 			 */
 			lastUnreadMentionBelowViewportIndex: null,
-			preventFindingUnread: false,
 			roomListModifiedBefore: 0,
 			forceFullRoomListRefreshAfterXLoops: 0,
 			isFetchingConversations: false,
@@ -661,6 +660,16 @@ export default {
 			return sortConversationsList(this.filteredConversationsList, this.groupMode, this.sortOrder)
 		},
 
+		unreadMentionIndices() {
+			const indices = []
+			for (const i in this.sortedConversationsList) {
+				if (hasUnreadMentions(this.sortedConversationsList[i])) {
+					indices.push(i)
+				}
+			}
+			return indices
+		},
+
 		emptyContentLabel() {
 			if (this.showThreadsList) {
 				return t('spreed', 'No followed threads')
@@ -752,7 +761,7 @@ export default {
 		},
 
 		showEmptyContent() {
-			return (this.conversationsInitialised && !this.filteredConversationsList.length)
+			return (this.conversationsInitialised && !this.sortedConversationsList.length)
 				|| (this.showThreadsList && this.followedThreadsInitialised && !this.followedThreads.length)
 		},
 	},
@@ -770,6 +779,10 @@ export default {
 				this.chatExtrasStore.fetchFollowedThreadsList()
 			}
 		},
+
+		unreadMentionIndices() {
+			this.debounceHandleScroll()
+		},
 	},
 
 	beforeMount() {
@@ -817,7 +830,7 @@ export default {
 	mounted() {
 		this.debounceFetchSearchResults = debounce(this.fetchSearchResults, 250)
 		this.debounceFetchConversations = debounce(this.fetchConversations, 3000)
-		this.debounceHandleScroll = debounce(this.handleScroll, 50)
+		this.debounceHandleScroll = debounce(this.handleScroll, 100)
 
 		if (supportTags) {
 			// Fetch conversation tags
@@ -914,17 +927,10 @@ export default {
 			this.searchText = ''
 			// Initiate the navigation status
 			this.isNavigating = false
-
-			this.handleUnreadMention()
 		},
 
 		scrollBottomUnread() {
-			this.preventFindingUnread = true
 			this.$refs.scroller.scrollToItem(this.lastUnreadMentionBelowViewportIndex)
-			setTimeout(() => {
-				this.handleUnreadMention()
-				this.preventFindingUnread = false
-			}, 500)
 		},
 
 		async fetchPossibleConversations() {
@@ -1142,33 +1148,29 @@ export default {
 		},
 
 		handleConversationsReceived() {
-			this.handleUnreadMention()
 			if (this.$route.params.token) {
 				this.showArchived = this.$store.getters.conversation(this.$route.params.token)?.isArchived ?? false
 				this.scrollToConversation(this.$route.params.token)
 			}
 		},
 
-		// Checks whether the conversations list is scrolled all the way to the top
-		// or not
 		handleScroll() {
-			this.handleUnreadMention()
+			this.computeLastUnreadMention()
 		},
 
 		/**
-		 * Find position of the last unread conversation below viewport
+		 * Find position of the last unread conversation below viewport.
+		 * Iterates only over indices with unread mentions (cached via the
+		 * unreadMentionIndices computed) instead of the full list.
 		 */
-		async handleUnreadMention() {
-			await this.$nextTick()
-
-			this.lastUnreadMentionBelowViewportIndex = null
-			const lastConversationInViewport = this.$refs.scroller.getLastItemInViewportIndex()
-			for (let i = this.filteredConversationsList.length - 1; i > lastConversationInViewport; i--) {
-				if (hasUnreadMentions(this.filteredConversationsList[i])) {
-					this.lastUnreadMentionBelowViewportIndex = i
-					return
-				}
+		computeLastUnreadMention() {
+			if (!this.$refs.scroller) {
+				this.lastUnreadMentionBelowViewportIndex = null
+				return
 			}
+			const lastInViewport = this.$refs.scroller.getLastItemInViewportIndex()
+			this.lastUnreadMentionBelowViewportIndex = this.unreadMentionIndices
+				.findLast((idx) => idx > lastInViewport) ?? null
 		},
 
 		async scrollToConversation(token) {