I found this question from a few months ago, with a non-working solution: FACEBOOK - Typing a comment causes the screen to scroll on its own.
This only happens when using FF as I have used both Brave and Opera without any issues. When I am typing a reply or comment (not a new post), as soon as I hit backspace, the screen jumps to the bottom of the feed and I can no longer see what I am typing. It I enter a few blank returns, it jumps to the top of the screen and I also can't see what I'm typing. If I add an emoji it also jumps to the top or bottom. This started about a week ago. I just updated the browser hoping it would solve the problem - and it didn't. I already tried the recommended solution of checking the about:config, browser.backspace_action settings and they are fine. What else you got? Thanks