Firefox foar Mobyl-mienskipsfoarum

I assume I've found a bug when trying to minimise the video on YouTube turning into picture-in-picture, which exits fullscreen and the navigation bar gets in the way, but it's fixed when I sign out of my account(s).

Whenever I enter picture in picture mode on YouTube it exits full screen. It didn't use to do this but started doing it a few weeks ago and this prevents me from actually being able to use picture in picture properly