Looks like multiple changes occurred at the same times. Making it even trickier to fix. I remember few years back the Mozilla/Android/Firefox folks reintroduced these AirMouse problems. It took a while to fix. After spending the evening researching, I'm starting to feel we might have issues on both ends (Apps AND OS). And since I'm not technical enough to word the bug narrative properly, it's hard to be taken seriously. I opened on bug on Mozzilla/Android/Firefox yesterday and they closed it 5 seconds later, refering it to an open since 2019 Chromium bug. If it's known and unresolved since 2019. They why the heck everything was fine until I updated my U22 to 005FW. :-( I think I'm gonna cry.
Unfortunately, the problem does not concern only browsers but many other apps. I think the problem can be solved by Minix / Amlogic at the firmware level ... in this thread it emerged that other Android 9 boxes do not have this problem.
Marty also analyzed the firmware of the android 9 box with working scrolling and found out what could be causing this problem and invited MINIX - John, MINIX - Martin to investigate with the Minix / Amlogic developers.
I have not yet installed the 005 firmware (I tried but the update was not successful and now the box does not start anymore, always remaining in recovery mode even restarting the box, I have to try to load the new firmware manually) but it seemed to understand from your comment that the problem has not yet been solved.
Since the developers do not comment on this problem I wonder if they intend to solve it or not ...