Okay, I’ve got 2 screenshots that should help.
1: Opening the tab, seeing 1d old topics.
2: Clicking on ‘See 21 new or updated topics’ (now the correct view).
A side effect of this bug is that I would get a random (3) supposedly new topics (or any number), but disappears when I choose New in the topic list.
UPDATE: Curiously enough, after leaving the tab and coming back immediately after, although I was right at the top of the topic list, it suddenly jumped to around the topics in the 1st screenshot.
Here is a screen recording of the issue (ignore the bar at the top and the lines on the screen).
Thankfully, a reload gixes this last problem, but not the original one.