So for some time now since the nether update came out I've been crashing a lot. And recently i just figured out some possible causes. If a player stands on top of a shulker and looks down and opens it, to other players they will become invisible and if the host is nearby it will cause them to freeze and stay like that, forcing them to close the game which has caused issues with saving. One example is i was in the nether and I had placed a shulker and my friend opened theirs and it caused me to freeze so i closed the game and when starting the world the shulkers were not placed anymore and were missing from our inventory. I originally had this issue on my world on Windows but my friend just had this on Xbox One.