XBOX One X Series X - Unable to play any world or join realm plus complete shutdown

I installed Minecraft on my new Xbox One Series X after Christmas. During the first play the Xbox crashed and completely shut down (not just the home screen but I had to manually restart - like it lost power completely).

Now when launching Minecraft I get to the "Play" screen but choosing any saved world gives an error message: "There was a problem with this world" and nothing happens.

In addition when trying to join my own REALM Minecraft just freezes and then drops me on the home screen.

I already reinstalled the entire game with no effect.

I do not have any further idea how to get Minecraft going again on the Series X - any help or advice is appreciated (maybe this is a known issue?).

I found related issues from other players:
https://bugs.mojang.com/browse/MCPE-112144
https://bugs.mojang.com/browse/MCPE-112285