Whenever I join my realm, I get your typical loading screen then enter my world. I manage to be able to walk around for five to ten seconds before getting the disconnected screen, hearing from my servermates that the world crashed, and having our progress be reset to the last backup. No error message appeared.
If it helps, the server is vanilla, no mods or even textures added. No specific error message has happened. Everyone else can access just fine, and I am the only one ever having issues. I have checked Reddit and Minecraft Forum too, and many people have this same issue. I can join other people's worlds and the bedrock servers fine. I am unsure why nobody has reported it. I am duplicating this issue, because as far as I am aware, everyone is ignoring this. IF A VIDEO OF THE CRASH WOULD HELP, I CAN GET ONE THIS WEEK.
Thank you for your report!
However, this issue is Invalid.
Crashes such as these are logged automatically by the game or realm server and investigated further by the development team internally, so they are not generally kept on the bug tracker.
If you can provide a list of steps that someone else can follow to reproduce a crash then feel free to create a new report. Please be sure to always search for duplicates before creating any new report. Please see the Bug Tracker Guidelines for more information.
Sometimes when a crash occurs the world will revert to a previous saved state. This specific issue is tracked as MCPE-12347.