I have a similar problem, when I try to replace the realm world it loads completely and says it worked but then goes back to the initializing upload screen and does nothing. This is on a 5th gen fire tablet.
Well that was a simple fix
I have a dragon touch y88x pro, I think the version is the 16.40 hotfix, and I have the Xbox app and already have an account from a 5th gen fire tablet. I had also tried uninstalling and reinstalling minecraft and Xbox in a bunch of different orders but it still just crashes.
This bug is also on android 9, same problems everyone else is listing
I started having this problem in the last month, I have no idea how or why it happens but it started after I built a villager carrot farm, but after taking it down it still happens, the way I've been fixing it is getting off and back on the world, some other effects are blocks not making particles and not dropping the item when broken, and you also can't open your inventory, I'm on a tablet with android 9