I recently had a save game fail silently when the disk filled up.  I saved the game as always, got no error, and exited the game.

When I came back to play again, I got a "save game file is not compatible with this version of the game" error. 

Turns out that the disk filled up (the save game file was significantly shorter than the previous saves).

Some changes to behavior would be desirable:

- Proper error checking when writing save files, and displaying an error that says "Error writing save file: disk full error", so we know to address that problem before exiting the game and losing our progress.

- When overwriting an existing save game file, write out a new file first, verify that it succeeded, and *then* replace the old file with the new.  This protects against destroying the old save game before the new save game is safely on disk.

- A less confusing error when the save game file is corrupt/truncated.  The error was misleading; a simple checksum should easily be able to tell if the save game file is valid or not, and can report *that* instead of the 'incompatible' error that suggests something else is going on.

I also note that the auto-saves had not triggered for over a month.  Auto-saves were set to occur every 5 turns.  I assume that because this was late in the game and I never played 5 turns in one sitting, that auto-saves never occurred.  Or does the auto-save turn counter reset to zero each time a manual save is performed?  If auto-saves could occur every 5 turns regardless of manual saves or whether I've returned and re-loaded, that would be grand.  Without the autosaves, I have to go back to a save game that is over 10 gameplay hours older than the corrupted save game file.