I experienced by "verifying integrity of game cache" it reports: "one corrupted game file ordered again" (translated by my own words from my origin language- so I expect the report to differ in english). I rechecked (verified again) and report was fine. 

After one more turn ingame same message appears, if I verify integrity of game cache again and so on. I asked my friend to do same and he has same report after every turn verifying integrity of game cache.