Thanks for sharing the videos that was really helpful. As I was watching the 'genre skip' I noticed that you were scrolling vertically down while on the 'left most' movie. Do you see this behavior still if you swipe to the right so you're on the right side while scrolling down? As a fellow Siri Remote user I know it can be easily to accidentally swipe horizontally when trying to scroll vertically and I'm curious if that's happening here.
The Movie Genres view is an out of the box Apple provided thing so it's handling all the scrolling and focus behavior and we have nothing as far as I know that would get in the way of that.
For the issue of randomly bouncing back to the top I'll have to see if I can reliably repeat that on my end. If I can I should be able to find the issue and get a fix out there.