I have the same issue; but I have not identified if it is a specific world.
At some point a few weeks ago, my account just stopped syncing to cloud.
I deleted a bunch of saved games, and followed all current reset guidance, yet still on my Microsoft account it fails to sync. Usually I get hung before the "play" button appears; if I go offline I can continue to play.
I will continue to delete saved games and worlds, in hopes this IS the problem. I wish there were better diagnostics on XBox so I could send a specific error code.
I just renewed gold so I could netplay too - and since this sync issue happened - I can't play with friends.
After a long conversation and triage with Microsoft, it looks like this is a Mojang issue.
When a world is being synced to cloud, especially if it is a big world, there is a possibility that the world is corrupted. For example, power goes out, internet goes down, etc. This leaves the world in a bad state in the cloud. You can continue to play offline with the local save data; but you will get fail to sync errors if you try to log in online. If you are logged in before you see the Play control, Minecraft just spins its wheels on the rotating world splash after you hit cancel after the failed sync error. If you log in after you see the main screen, you get a sync error, but you can continue to play the local copy. The trouble is, if you can't sync, the game seems to assume your account is in a bad state, and you see the Oops! your disconnected error and can't play with anyone.
The solution is to delete the offending world locally (even if you just spent 3 months building like me).
Minecraft needs to "fail open" if there is a sync issue on bad world data. One bad world should NOT take down the entire game and sync process. Previous Jira have said its "Microsoft's problem"; but the sync flow is actually Mojang's. A better design would be to allow a flag on a world for sync or not... or some way to navigate and purge the BAD data in the cloud (because the local storage is still good).