Never had a problem with the extension until now, since the last update when i am in full screen mode the video isn't taking the full screen space (3840*2160) , instead i have a grey border that i can't seem to remove.

Edit: Changing my review to 5 stars because I now think this issue comes from Youtube itself and not the add-on

Beside this issue the add-on is great, as i said never had any problem for years before Youtube decided to mess up the UI.