Unreliable unread marker

[free-electrician]

Describe the bug

As of recently the 'Jump to Unread' button does not always appear upon clicking on a room. Instead the badge with the number of unread messages disappears immediately. The only occasion when the read marker reliably appears is when there are not a lot of new messages and so the marker is not off-screen.

Reproduction

Click on a previously joined room with unread messages
Observe how sometimes the 'Jump to Unread' and 'Mark as Read' buttons are missing and the badge with the number of unread messages next to the name of the room disappears

Expected behavior

Click on a previously joined room with unread messages
Both the 'Jump to Unread' and 'Mark as Read' buttons should be visible and the badge with the number of unread messages should only disappear after clicking on the 'Mark as Read' button

Platform and versions

OS: MacOS, Fedora
Browser: Firefox 131.0.3, Safari 18.0
Cinny version: 4.2.2 (app.cinny.in, dev.cinny.in, Flatpak app)
Matrix homeserver: matrix.org, matrix.arcticfoxes.net

Additional context

No response