I'm having a new problem with Firefox, which I think appeared with Firefox 84 (but I'm not 100% sure). When I type in some text boxes, the cursor gets very slow and unres… (read more)
I'm having a new problem with Firefox, which I think appeared with Firefox 84 (but I'm not 100% sure). When I type in some text boxes, the cursor gets very slow and unresponsive to move around by the keyboard _if_ the text in the box is long enough so that a scrollbar appears on the right hand side. Sometimes. It doesn't happen at all sites -- it's not duplicating in this textbox that I'm typing in right now -- but it happens all of the time in the message boxes at playdiplomacy.com, and sometimes on GitHub.com when posting issues. Sporadically and unreliably.
As far as I can tell, the cursor is still moving quickly and responsively, but the blink itself isn't happening so I can't see it. If I hold down the left cursor key, it looks like the cursor isn't going anywhere, but if I hit a letter key that letter appears instantly at the location where the cursor has apparently moved to, with no delay.
The problem does not occur when I hold down shift (to highlight) while moving the cursor via the arrow keys, which further suggests that it is somehow related to the cursor blinking.
Restarting in safe mode makes the problem go away instantly. Disabling all add-ons myself does not. Starting with a brand new profile does _not_ make the problem go away either. So there's something safe mode is doing that a new profile doesn't.
Any idea what might be causing this?
(Ubuntu 20.04, Firefox 84.0).