On xbox splitscreen is not working on worlds that have been previously started before the recent update when going on first player in a world that has already been started

If player one has stuff in their inception has stuff in their inventory and a second player joins splitscreen then player 2 will no longer have any stuff and will "restart" whoever joins second all their stuff is erased unless they join first player where they will have their stuff back in their inventory. Please fix Mojang me and my brother play on a realm all the time together.