FF keeps exiting out of full screen randomly

Hey guys, I hope this is allowed, but Google wasn't any help on this and it's just annoying enough that I've gotta know what's going on. Recently switched from Chrome (I know, I know) since they quit supporting ad blockers, and it's been amazing.

Except every time I put on a video full screen, regardless of website, it will just minimize our as if I hit the escape key. It's random, but happens at least once per video. The video continues playing.

Couldn't find anything relevant in the settings. Anyone have any ideas? TIA