So far it appears not to be an issue anymore!!
This is a new world, no realm.
No, I am not on peaceful, one which will spawn and only one which
I also have this issue, or something similar, that is, minecraft keeps crashing after I convert a world from XB1E to the new Bedrock/Better Together. Even when I was able to convert a world, before the current 1.2.3.6 update, that game world also crashes. In both instances, that is, 1) converting a old world crashes and 2) current worlds crash, my entire xbox becomes unusable and requires a hard reset. Thanks Mojang for all your continued efforts to make this game enjoyable
I also have this issue on XBOX ONE, I find that copying a world reverts your save game to a previous state as well as "Save and quit" I seem to be able so far to get around this by not saving at all and not even exiting minecraft but by closing it with another xbox game
I am also having this issue on a convert world played as a realm, mob spawner works then the icon disappears and no mobs will spawn but there are flames