Continuity mistake: During the first few episodes the name of the painting changes from The Reclining Madonna to The Fallen Madonna.
Pigeon Post - S1-E3
Continuity mistake: The size of the paper Rene uses for the pigeon grows substantially when Herr Flick find it near the end of the episode. (00:19:45 - 00:29:20)
Continuity mistake: When Rene comes upstairs to speak to Michelle, his hands and arms are covered in cement. However, when he arrives in the cafe from the basement his arms and hands are clean. Not enough time has elapsed for him to clean them all perfectly. (00:03:05)