Thanks I had missed that. Last I had read there was a comment about being hard to reproduce. Thanks for the update.
I’m having the same issue - but on the full list of movies, where you scroll down in alphabetical order.
If you hold down to keep scrolling to a different letter further down the list (for example - 500 movies from A-Z, starting at A, but long press down to scroll down to get to S), it allows you to scroll down and stop - but then whatever you do or press, it immediately jumps back up to where it was before you started to long press scroll - so you can no longer long press scroll, you have to keep pressing down, down, down, down…
This is on Apple TV 4K
This should be fixed in today’s 8.4.3 update. 
Yes, it’s fixed indeed. Thank you Firecore team!
I can confirm this has fixed the scrolling issue in movie selection (scrolling movies A-Z, lost press scroll).
The issue was that when you long press scroll, and get to another letter, as soon as you then pressed anything it would just straight back to where it was before.
This has now been fixed and you can scroll and long scroll as normal and it will stay wherever you scroll to, without jumping back to where you were.
Thanks for fixing this.