Other mistake: About two-thirds of the way in, Robert Young re-visits the 'scene of the crime'. While climbing up the steep bank from the ravine, he reaches the top and, and in a very short shot (a few seconds), his shadow is cast upon the painted background scenery.
Continuity mistake: Pinkie sweeps all the glasses on top of the bar onto the floor, yet after he and his gang have gone we see broken glass on the bar top.
Revealing mistake: When Joan Crawford shoots van Heflin, he reacts as if he was shot before the shot is fired.
Plot hole: Early in the movie, when Joe Stefanos tells Mary, the owner of the luncheonette, that he found Jeff Bailey by passing by and seeing the name on the sign of the gas station, it makes no sense. He only knew him by the name Jeff Markham. Even if he was just lying to her, he uses the same explanation when he is alone talking to Jeff. We never know how he found him.
Suggested correction: He told Jeff that he saw him pumping gas at the station.
Continuity mistake: When the stunt person for character Mrs. Kraft rolls horizontally down the dune, the stunt person's head is pointed west, but the scene picks up with the character's head pointed east. (01:10:00 - 01:13:00)
Continuity mistake: When Robert Taylor escapes from the asylum, and is driving the second car he steals, the car is shown at least once with windshield wipers pivoting from above the windshield, then shown with the wipers pivoting from below the windshield. Clearly, these are two different cars. I think the studio borrowed wiper footage from the scene in which he is driving the first stolen car, to use at moments in the scene in which he is driving in the second car.