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.
Other mistake: When we see the Church Hymnary being opened, the date on the left-hand page is signed by Margaret in 1928, but the book is dated 1932.