Continuity mistake: Right at the end, the insurance man gives Charlotte Jewel Mayhew's letter and in the next shot of him, his hands are empty. But in the following shot he's holding the letter again.
Continuity mistake: About 25 minutes into the film, Vincent Price puts two vampire bodies into the back of his station wagon. Viewed from the open rear door, the woman is on the right side face up and the man is on the left side face down, and he drives off to the pit. In the next scene, he parks the car at the pit and when he goes to unload the bodies, the woman is now on the left side face down and the man is one the right side face up. For people who have died and then been killed again, they sure did move around a lot in the back of that car.
Other mistake: There were no gorgons named Megara. The three that existed were Medusa, Euryale, and Stheno.
Continuity mistake: At the ring toss booth, there are five rings on the bench as one of the booth attendants is counting coins from the till. When the other booth attendant turns to give Leo the doll he won, the rings disappear, then reappear.