Ghasts in Nether able to attack player in Overworld in Multiplayer

As there's no dedicated MCPE server, I run a Win10 MCPE session with a "dummy"/stale host avatar, then we all connect to this session. Works fine as server, been using it for 20+ hours since 0.12. The host avatar is locked in a small lit room in the Overworld.

Since 0.13 however, this host avatar regularily started dying for no apparent reason. Earlier today I discovered that he suddently catches fire, takes damage and dies, though there was absolutely no reason this should happen(???)

Then tonight while I was walking through a closed tunnel in the Nether with my regular avatar, I suddeltly heard the sound of Ghasts launching fireballs. I was very puzzled, as there was no way they could see me - but even more puzzeld when I heard the fireballs explode and watched the the host avatar on the other screen cathing fire and die!

I respawned him and the exact same thing happened. The Ghasts attacked and killed him.

I walked my regular avatar through a portal the Overworld and the problem disappeared. I walked back and the host was instantly attacked.

I can reproduce this consistently.