When selecting clips on the timeline, if your cursor hovers over the time ruler numbers there's a small section where selection will just completely drop; moving further up or back down will reselect everything. This can be a little annoying when trying to just select everything on your screen as you may accidentally go too far up (especially if you do a little upward flick like me) and it just randomly unselects everything. I can't really see a particular reason for why this might be happening and it doesn't line up at all with where you're able to right click vs not.
Clip is from the current 25.4 beta but the issue isn't currently present on 25.0/25.1 (I don't have 25.2+ installed on any systems so can't test that)
Tested on Windows. Clip attached to show the issue