Continuity mistake: In the first club session, where Winkelmann presides, a pair of glasses appears in the pocket of his jacket right before he puts them on. (00:10:55)
Continuity mistake: In the scene where Winkelmann and Mrs. Tietze try to make the Melzers change their sofa upholstering to something less depressing, they step out to have a private talk and end up in a muddy flower bed. When they walk back in they don't leave any marks on the terrace but heavy mud prints on the living room floor, although Winkelmann's shoes look spick-and-span after he sits down. (00:25:55)
Continuity mistake: When Winkelmann, Tietze, and the Italian agent drive off there's a wild load of furniture on the rooftop. When they stop over at the latter's brother-in-law's estate the furniture arrangement has changed completely. (00:42:40)
Other mistake: Winkelmann has the habit of confusing floors, thus trying to open his neighbor's door. When he returns home after the club session he, therefore, checks the name on the mailbox before he opens his door, but this name is much to short to be his (it's safe to assume it's not his nickname Pussi). (00:14:00)
Continuity mistake: When Winkelmann enters his shop near the beginning of the movie there is something like a security sticker on the right side, but when the camera cuts to inside the sticker is gone. (00:03:20)
