Goofs

Vicki's hair changes length constantly, sometimes in the middle of a scene.

Susan's pants change color sometime between the 30 foot gorilla and the devil's attack.

David's shirt alternates between being buttoned and unbuttoned. His undershirt disappears and reappears.

Jim is shown wearing, then not wearing, a belt throughout the movie.

Jim's sweater appears and disappears throughout the film. His sideburns also change lengths throughout the film (these can be attributed to the combination of footage from the original film to the scenes added to the 1970 version).

Why would bother picking the lock to the briefcase when he could have simply cut the strap.

Near the end of the film, the camera begins spinning during an action scene. For a few frames the foot of the cameraman is visible. The foot may actually belong to renown actor Ed Begley Jr., who served as an assistant cameraman on the shoot.

At the beginning of the movie, before the main character is hit by the car (the one that supposedly has no driver), we can clearly see that someone is driving while the car approaches, but when we see the inside of the car, there's no one driving.

Just after Susan is picked-up by the Asmodeus demon, the next shot is the camera swinging around subjectively and the foot that appears in the shot belongs to Dennis Muren who explained, "I honestly didn't expect anyone to notice it".

Support wires are visible on the Taurus figure and rocks during the rock-throwing sequence.