Revealing mistake: In the very early scene in which Zed points his revolver directly toward the viewing audience and shoots, it's visible that there is no ammunition in the gun's chambers.
Revealing mistake: When Herbie dives into the ocean, water can be seen coming out of the open back window, even though the next shot shows the inside completely dry and the window closed.
Revealing mistake: When Julie begins running up the large flight of steps, a man can be seen standing on a balcony to the right of shot. He can be seen watching Julie run up the stairs and then immediately turns his head to his left to glance at the camera. (00:09:20)