Youtube is really slow when going fullscreen/back to window mode

Description of the issue:
When I have movie on youtube opened (doesn’t matter if it is stopped or already playing) it takes fovever (2-4 seconds) to go into fullscreen. Everything is really slow, almost freezed. I noticed that today, never occured before (but I use Brave for few days). When I go back to window mode it is same, all interface is loading really slow. I have tried to disable the brave shield and any extensions I have (ublock, privacy badger, auto HD etc.), didn’t help, nor clearing cache. The problem doesn’t occur on Firefox for example. I have noticed that it is much worse when I have “Playlist” ‘widget’ extended (I have 150 movies in ‘watch later’ list) and when I minimize this widget it’s getting better. But still, I didn’t have a problem with that day or two before. Also, operation on this playlist, like for example deleting a video seems to be slower.

How can this issue be reproduced?
Just open a YT video from a playlist with some movies on it, probably the more videos on playlist the worse it gets.

Expected result:
To run YT faster.

Brave Version:
1.9.80 Chromium: 81.0.4044.138 (Official Build) (64-bit)