I'm experiencing some strange behaviors with my YT app recently.
When pausing a video and continuing, the sound keeps playing normally, but the picture, freezes for a second and kind of fast-forwards quickly (like double the speed) to catch up with the sound.
Also, sometimes, but quite often, YT seems not to stay idle in the background when browsing other apps in the meantime. When I want to come back to YT, it loads like it was opened for the first time, and shows the "logged in as ..." dialog.
I've been seeing this a fair amount myself lately on my Mi Box S. Annoying but not the end of the world since we mostly use it to watch stuff where it's a talking head, so to speak. I haven't been able to fix it via any cache clearing or the like, however.