Second Player entering crashes world

Hi, I have a survival minecraft world on Bedrock Beta Edition on Xbox One.

My son and I share this world and regularly play together on it. However, since the xbox system update on the 4th November, whenever he attempts to join my world it crashes and boots us both out upon him signing in.

We have tried other accounts and they all seem to be able to share my world, although one player always remains invisible to the other player. Which never happened before either.

For some reason it is unique to the one account that it crashes when we both try and use it, and just before it crashes it comes up with a black window that says 'Let's go'!.

When other players join this message does not appear, and it is right when this message appears that it crashes.

I have checked that there are no age restrictions and player is set to unrestricted, player has also been sent and accepted an invitation, we have tried unsubscribing both accounts from the xbox and adding them fresh, we have checked parental restrictions are not in place for any of these accounts, the world is set to accept players.

We have tried everything.
Microsofts reply to this was that it is a minecraft issue, not a microsoft issue.

It has always worked, and now it just doesn't even though we have made no changes.

Any assistance greatly appreciated.