Iron goes missing. Boats and mine carts invisible for one player and not the other.

I’ve been playing on split screen with a friend and we’re having some very aggravating issues. Mobs have been freezing. We’ll be fighting them and then they’ll just freeze for a while. Boats and mine carts will vanish for one player. We’ll both be looking at the same spot and she’ll see the boat/mine cart, but I won’t. The most annoying one is that our iron keeps vanishing. We made a bucket and put it in a chest. When we went to get it, it was gone. She had a hopper and a bucket on her character. We left the game and when we came back she was in a completely different location with everything she had on her, except the iron. It’s hard enough to find iron. We don’t need it disappearing too.