The stake in skeleton's chest wasn't in position it's shown when it's taken out to be used as a murder weapon.
When hypnotizer is killed, he falls, but no stake can be seen on his back. Then it appears as he's seen lying on the floor in the next shot.
Position of the vampire changed after he is killed, at the first shot of his decomposing.
Obvious cuts when Waldemar's transformation begins near the end of the movie.
Waldemar obviously moving his eyes in the grave even though he is supposed to be immobilized by the silver bullet.
Waldemar moving his eyes during the operation even though he is supposed to be immobilized by the silver bullet.
Obvious still used for a close-up of dead Carl.
Obvious paint used for Frankenstein's monster's face. It disappears further on his neck and on the back of his head and normal human skin is revealed.
Obvious fake moon shown before Waldemar's first transformation.
Warnoff says Frankenstein's monster doesn't have a heart, but it actually does and wasn't a being not capable of emotions and thought as he describes it.