There is also a problem with watchers causing you to disconnect because you attacked an invalid entity.

@Mari065 To fix it you would have to edit the save and remove the item from your inventory manually.

Still an issue when running on a server, also happens when you try to create a hologram projection of yourself...

I got that error too when I hit my friend with the totem of possesion, I can't enter the server because the same error appears. Did you managed to solve it? And how?