I have the problem too. It seems the players on splitscreen are "linked" to the host as in they share items from a previous save, share endchest contents, and sometimes they even share taking damage. I'm worried if the items in my friend's inventories have completely disappeared or not and if they can be recovered. This problem is gamebreaking! Doesn't happen on all of my worlds though.
I walked back to my house when less than a minute later, it crashes. It stinks because my automatic farms requires pistons.
I noticed that the tridents don't even stick in the ground after being thrown at mobs. But if the trident is just thrown and doesn't hit a mob, it sticks in the ground normally and the player is able to pick it up.