When on a realm entering the nether and leaving will sometimes cause you to be stuck in the loading screen and it'll take a while to fix itself (hour/s). the end is slightly different: when entering or leaving the end or end cities it will cause you to be stuck on a chunk of not loaded in blocks and all you will see is the void and you cannot move. apon leaving the game and loading the realm back up, it will forever load and you can't go on until an hour or so has passed. myself and a friend experienced all these issues and i will provide an image where when we were stuck in the ends void. we were both stuck inside each other.