The license plates of Kathryn's car keep changing throughout the film. Sometimes they show "F" (Frankfurt), "HN" (Heilbronn) or "OF" (Offenbach).
Frank leaves Miriam curled up on the bed in her street clothes, asleep with a coat over her, while he goes down to explore the tunnel in the basement. When he returns, however, she is under the covers with a nightdress on.
Amount of feathers when boy is urinating at the beginning of the movie changes between two continuous shots.
The little sign in Miriam's car reads (in German) "Miriam - rennen nicht" - this is incorrect. "Miriam - renne nicht" would be right.
When Moebius throws that burning paper bag down the well in Miriam's cellar, you can see a stick attached to the bag, "sliding" it down the way. This had to be done, because the well was built horizontally to make filming easier.
The door doctor smashes is clearly fake, because the wood is visibly thin and too easy to break.
The opening scene states the year is 1970, but the song playing is America's "A Horse with No Name", which came out in 1972.
Miriam is supposed to live outside of Frankfurt, Hesse. In The end, the fire truck's license plate shows "F" for Frankfurt - but the policemen on site wear Bavarian uniforms (which is around 50-60km away).
The story is based in Frankfurt. When Moebius Kelly arrives in "Seligenstadt" (around 15-20kms outside of Frankfurt) the sign reads "Landkreis (county) Hoffenbach" - the county is called "Offenbach" in real life.