Other mistake: When the Creature comes out of the amniotic fluid bath, he slips around and then gets caught in the chains. Victor falls asleep and then there is a sequence of shots of him and the Creature running through the laboratory. In one shot, he is kneeling by the door and pulling on Victor's coat to wear and you can see large indentations in his back and sides. These look like a rubber or latex covering to enlarge his frame that have flexed the wrong way and have become concave and appear totally unrealistic.
Factual error: Justine is accused of murdering Victor's young brother and is taken by police. A lynch mob takes her to the top of a fortress wall, drapes a noose around her neck and tosses her over the side. She falls for what looks like at least 8 metres. When the rope comes taut, she is killed but her head isn't ripped off by the force of the fall. Falling for that distance should have torn her head from her body.
Revealing mistake: When Willie's body is covered, you can see the little boy playing him scrunch his eyes tighter shut and he smiles very briefly.