The problem is within the save game itself. During save, the xml for the game is saved into the save game. Basically once corrupted, that file is always corrupted. This method is what lets you finish older games even after patches. All the xml the save game needs is already in its file, the only way to use new xml is to start a new game. There is no validation/fixing of save games. Validation only checks the game files themselves, which a save game no longer needs.
To check if you have an actual bug:
Create a new game.
Play a couple turns.
Load this most recent game.
Hope I didn't make that too confusing.