My world saves and backups are not syncing on xbox single player no mods. I finally got an older backup to load and it spawned me at game spawn (0.x.0). I was able to make tools and build blocks. I updated builds and played for roughly 2 hours. Once I logged off I created a copy of the world I just worked in. Closed everything out and shut my xbox off.
When I logged in the next day it would not load either game save. It stated they were not synced and or corrupted.
Deleted local and storage saves as well as minecraft. Installed from the game pass app. This allowed me to open one of the save files only to start me off at original spawn again with my inventory gone.
This is only for pc there is no way to really dig into save files on xbox.