Plot hole: When Nosferatu is caught in the sunlight towards the end, his reflection can be seen in the tall standing mirror in the corner of the room. This makes no sense because vampires do not cast reflections. Deliberate or not, in the original Bram Stoker novel, there is a scene in which the character Harker is shaving, and is disturbed to see that the Count casts no reflection. There is also a passage that states, "He throws no shadow, he make in the mirror no reflect." Some would argue that the rising of the sun robs him of his powers, giving him the reflection. But his reflection is visible before the rooster starts crowing, before the sun even rises.
Suggested correction: That's all from the book, none of that is established in the film.
Continuity mistake: In a scene set in 1862, Harold Lloyd portrays his own grandfather, a Confederate soldier. An elderly woman gives him a tiki-like lucky charm which she says will protect him as he confronts leaders of the Union Army. After he successfully fights off two soldiers he holds the charm in his left hand, but the close-up shows the charm in his right hand, then it's back in his left hand in the next shot.