It is most likely due to save file being locked by your OS somehow (could be anything from anti-virus or cloud service) Try turning these off to see if it helps
Here is a another possible solution. First navigate to the .exe file (Right click game in steam library->Manage->Browse local files)
1: Right click on the game (.exe)
2: Property
3: Compatibility
4: Compatibility mode -> Windows 8
5: Apply