I love the extension, it is a must-have to enjoy youtube.
However, it is very broken on mobile right now.
After installing, in fullscreen, the video flips to portrait mode every 20 seconds or so. (Sometimes by itself, sometimes as a reaction to the screen being tapped).
The only way to fix it is to go out of FS or double tap to skip 10 seconds of the video.
It is incredibly annoying and by rating one star my intentions are only for the dev to give the issue the appropriate amount of attention it deserves as I am not the only one who suffers from this problem.
There is an unresolved github thread about it and there are reviews here that mention the same issue.
As soon as it is fixed, I will five it the 5+ starts this amazing extension deserves.