Continuity mistake: In the scene at the end where they are finding out who the killer is, Joshua has lots of blood on his face. In next shot, there is less of it and then it disappears in the next shot. Then, there is lots of blood again.
Factual error: When Joshua and Il-sang Lee rush to the hotel to search for the stamps, they are in Clinancourt, which is a North suburb of Paris. In the next scene, we see them leaping into the train, and the station is 'Pyramides', which is a station in the center of Paris. They would have needed a 30 minutes ride and at least one train to change to get from Clinancourt to Pyramides.
Factual error: The first scenes outside the hotel where Regina is staying were filmed in some area very typical of the 8th arrondissement of Paris. In the end, when Joshua and Il-sang Lee rush to that hotel to get the stamps, they get off at Chatelet, which is in the 1st arrondissement. A few scenes later, they rush out of the hotel, run for less than a minute and find themselves in a desert street which can exist neither in the 8th nor in the 1st arrondissement. It was certainly a street in some remote Northern area of Paris.