my problem from the get go
This was the film that threw out the logic established in the previous films. They clearly state in The Wolf Man that you can destroy a werewolf with a silver weapon, and they do, twice in the film. In this film, suddenly he's back from THE DEAD! Why? How? Why didn't he come back to life in his grave earlier? There were other full moons since his father killed him. And in the previous film he transforms without the moon passing over his body, so it's not that.
It's interesting that the clever continuity they did keep, casting Lugosi to play Igor/Monster, is the thing they cut. Dumb.
From here it was just downhill.