My friend is host on our server he has not that problem but we as member have it. When I want to put something in my storage the hole stack is duplicating in every empty slot of the storage. It´s a bad way to cheat.
I often have a completely black screen after sleeping on my multiplayer server. I can still see my mouse cursor and hear the game, but I'm left to exit to the main menu and reconnect. The other player doesn't have the problem when it occurs to me.