Frequent Crashes in Multiplayer

When trying to play multiplayer, the game frequently crashes,closes or looses connection.

I try to play with a dedicated "server-phone", which should host the world via LAN. TIll 0.13. this worked quite well (till we stopped playing being frustrated about disappearing mobs)

With 0.14b3 , the game frequently closes down. Some times (1 out of 10), the client will reappear in a cave without any inventory - i suspect it to be at x:0,y:0, but can't confirm, as i didn't dig up there without any pick axe...

Sometimes, the last changes made by the client aren't visible when the world is reloaded.