I've been playing Bedrock survival with my wife for a while, and I have always been the host.
A few days ago a problem started occuring, where my wife tries to join our world, but the game disconnects for her.

We only use Vanilla BDcraft resource packs, and nothing else.
She joins in, I get the message ingame, but the game freezes for her, and gets DC'ed a couple minutes after. 

Single player works just fine, and if she hosts the game, the problem doesn't seem to be there.

We tried several workarounds for this, as first the problem seemed to be with her NAT type on XB1. I fixed it with a couple portforwards. We're both using wired connections on the same network. Nothing seems to work as of today.