When Alan is caressing tied Betty, his wound is dry, yet when he is shown touching it in pain, it's wet.
Each scene with Betty having the pins taped under her eyes, there is an inconsistency regarding the placement and amount of blood shown. Sometimes there is a lot, then a little, and then none - changing back and forth.
Spikes taped to the cheekbones, as shown, would not move when the eyes closed, as claimed by Betty's torturer.
In the killer's POV shot entering the costume workshop, the camera and camera dolly are seen in a mirror on the right.
During the shootout in Betty's apartment as the masked killer dives out of the way of a shot, and the camera quickly pans after him, a crew member is visible on the right side of the frame, trying to get out of the way.
When in the wardrobe studio to repair the damaged dress, the wind is blowing on sheets of fabrics laying on the floor. While the camera is traveling forward, it pans to the right, and the camera crew is visible in a mirror's reflection.
During the chase in Betty's apartment, as the killer runs POV through the house the camera tilts back and forth showing for a brief second the top of the set in Betty's room and the space above it. Also, while exiting the bedroom, lighting equipment is visible on the left side of the frame.