Encountering stuttering/low frame rates on the pop-up video in fullscreen mode. This DOES NOT always happen but is more apparent if other tabs are open and you browse other tabs before coming back to the pop-up window and entering fullscreen.
How to replicate:
(1) Go to youtube
(2) Play any video, preferably 1080p50fps or 1080p60fps
(3) Pop up the video in the pop-up window.
(4) Double-click on the pop-up window to enter fullscreen mode.
(5) Video stuttering will sometimes be observed.
Again, I only noticed this happening in this version. Previous versions were all fine.