Revealing mistake: Fight in the toilet of the Paris nightclub: the presumed Lark rips out the sink's drain and begins assaulting Tom Cruise with it; Walker intervenes holding him, but the nimble Asian does a flip and brutally tosses him to the ground. As Henry Cavill is bent over before being snapped to the floor, on his back, you can definitely see a protective pad through the jacket. (00:31:52)
Revealing mistake: When the toilet fight is over, there's a pool of blood on the floor where Ethan steps on. However, he then moves around the place but leaves no footprints, revealing the blood is CGI.
Revealing mistake: During the bathroom fight and Ethan is starting to stand up from a urinal, you see his knee go into the foam padding that was used in the room.
Revealing mistake: At the end as Hunt and Walker are fighting for the detonator on the spectacular cliff (in actual Norway) they fall off, grabbing onto the rope suspending the helicopter. The issue being the rope moves too easily, revealing it was slack.
Revealing mistake: The helicopter that picks up Cruise after the final fight is registered as if it is Norwegian, even though they're supposed to be in India. The scene was filmed in Norway.
Answer: They are in France. The French word for police is "police."