I have had a couple of games reach what appears to be a state where they will not save.
What happens is that when trying to save, a message appears "Saving Game", but the in-game-menu does not automatically close.
Later when loading it becomes apparent that the previous save was quite a while ago. And recent attempts to save did not work, judging by file modified timestamps.
I have tried saving under various situations but once this happens it seems the only thing to do is to start again and hope it does not happen.