One really annoying problem is that, when I watched a few videos(the number varies), one video suddenly is not showed right because the sound is working, but the picture flickers.

Another, but less annoying, problem is one I want to explain with an example: When I open the menue(on the top of the screen) right at the beginning of the app(where you can see "Search", "My Channel" and so on) and choose "Settings", the menue is still open and does not close.

I hope I explained it well enough. When not, you're free to ask of course But anyway it's one of the best and useful apps!