TU24/1.16, CU14/1.17, TU27/CU15/1.18
Our world was created originally on PS3 and then enlarged from classic to small (borders maintained), from small to medium (borders overwritten), from medium to large (borders overwritten). We have man-made towns spread out in several maps across 7 saves (including the 6 world saves).
If we build in an area we have never been, it is only a matter of time before our world corrupts. It seems to be the save that isn't world data that corrupts perhaps when trying to generate a new save file (maybe world save 7? which never actually appears).
We can build just fine in areas that we've built in, but even that seems to corrupt if we build too heavily.
It is easily recreated in our save by travelling to any untouched section of the world and building a few buildings and trying to save.
If auto-save is on, the indication is how quick the autosave logo appears and disappears. If you manual save, the icon will not linger as long after returning to the game screen if the game has corrupted.
The world will also not copy using Minecrafts Main menu. This used to work. Now it will copy without a thumbnail (just the dirt block icon) and will refuse to load, making the menu noise when you try to select it. We've been backing up to USB because of this.
After the world has corrupted, Minecraft will not close properly and eventually crash.
Would really love to play on our beloved 24/7 server again.