Goofs

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.

The character of Judge Sternberg seems to be included for continuity from the previous film, Frankenstein's Bloody Terror (1968): The Judge claims that he had met Waldemar Danisnky and that they had both courted the same woman; it would make sense that he was Waldemar's romantic rival in the first film, a young lawyer who had aged while Waldemar, due to his apparent death, is the same. However, there are several problems with this theory: Waldemar's romantic rival in the first film was named Rudolph Weissman, not Sternberg. According to Sternberg, Waldemar had met a woman who later married Sternberg, before Sternberg himself; But in the first film, Rudolph and Janice are childhood friends, and Waldemar only meets Janice when she is an adult. Also, in the first film, Janice fires the silver bullet that kills Waldemar, and according to the plot presented by Warnoff here, a werewolf's death is final if the bullet is fired by a woman who loves him enough to die; Janice should have fulfilled this condition.

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.