When a world is "Opened to LAN" if a guest tries to ride a horse they are instantly kicked with an error "Internal Exception: Java.lang.NullPointerException". after that the same user can no longer join without getting the same error. also each time they attempt to join the horse they tried to ride is duplicated. (four retries resulted in 4 new horses and the player still could not join). only way to rejoin was to delete player data.