Continuity mistake: The crescent-shaped scar which bisects the protagonist's right eyebrow in many scenes appears instead on the left eyebrow in many others. Same size and shape, but looking as if photo-reversed; for instance, when his face appears from the darkness to sniff over the shoulder of the red-haired girl, the scar is in the right eye-brow. But during the scene in the plaza before a huge crowd (the hanging scene) the scar is over his left eye.
Factual error: The hanging is shown using the "standard drop", with a trapdoor, breaking the neck. This was not introduced until the 19th century (after France had abandoned the gallows for the guillotine), whereas the film is set in the 18th century. In those days the victim was just strung up on the gallows and left to strangulate (the "short drop").
Continuity mistake: In the first scene in Giuseppe Baldini's perfume shop, his employee comes in and starts setting three candles in a candelabra. He sets them very straight and upright, however after we cut to Guiseppe asking if he knows of Amor et Psyche and back to the shot of the candelabra again, all three candles are wonky. This is more than simple gravity could have caused.