The UI issues I've noticed aren't really bugs as much as they're intentional UI changes that happen to be poorly thought out. I'm used to Google randomly changing the UI for seemingly no benefit, but these changes are especially egregious considering how much of my youtube interaction is muscle memory.

For example, you used to be able to double tap just about anywhere on the screen to fast forward or rewind 10 seconds. Now on the first tap the bottom half of the screen becomes an overlay with a bunch of action buttons, causing the second tap to inadvertently engage one of the buttons.