I transferred a small 11MB world from my old xbox360 into my xbox1x (minecraft for xbox edition) and that went ok, I then opened the latest version of minecraft on the xbox1x (1.16.1) and start the importing of the old world, it gets to 44-45% then the background music stops, and it sits there for about a minute and minecraft then closes and the xbox goes back to its front screen. It doesn't show an error code. Maybe it creates a dump file and sends it to your servers ? , I dunno
I can copy the world off the xbox360 and email it to you so you can reproduce the issue if you like.
I can delete certain blocks on the 360 version if it helps ??,
The xbox360 is up to date as is the version of minecraft on the xbox360.

Many thanks
Dave.