17 days ago - AndrewT - Direct link
We can't help with modded games here I'm afraid.

If you both start a new campaign with NO mods at all enabled, do you still get this?

If so does it affect both local and cloud saves?  
16 days ago - AndrewT - Direct link
There is no logging of the game's attempts to write a save, by default. You could try enabling debug mode though.

I don't know anything about the structure of its save files - you might try user Mods for that.