Other mistake: It's the scene when Dr. Frankenstein's fiancee is being held hostage. To prove that she's all right, her captor allows her to talk to Dr. Frankenstein through a telephone type device. She's supposed to be tied up with her hands behind her back. But she pulls one arm from behind her for a fraction of a second, then tucks it back behind her again.
Suggested correction: While some may see this as a gaffe, consider this: Elizabeth is quite resourceful. She has been tied up in the cave for some time and has been working on freeing herself from her bonds, to the point of success. As Karl attempts to cover her mouth, she has a moment of panic and almost gives away how close she is to escaping. Remember, she does escape and gets to the watch tower just in time to make a plea to Henry to leave with her to safety.