I was playing in my survival world from my PlayStation  with my friends connected to it (one from Nintendo and the other from mobile) for quite some time until for some reason when we all exited the world it couldn't be saved. The game was stuck on the saving screen (see attachment) for at least seven hours and the world was still not saved, so I decided to close the app and see if it would load properly. Although it loaded when I reopened the world, all the progress we had made during out playing session had been lost.