Video Pop-Out seems to work find at first, until...
- ...you minimize the originating tab
- ...you go to another tab
- ...you scroll down until the originating video is out of view
At that moment the popped out video will start to stutter consistently while the audio keeps playing fine.
Fixes: either enable opera:flags/#d3d11-video-decoder or choose another graphics backend altogether at opera:flags/#use-angle