Visible crew/equipment: Chapter1: Purple Death. When Queen Fria says: "You see my friends, Ming has captured my general Lupi," you can see the shadow of the camera.
Flash Gordon Conquers the Universe (1940)
1 visible crew/equipment mistake
Directed by: Ford Beebe, Ray Taylor
Starring: Anne Gwynne, Charles Middleton, Buster Crabbe, Carol Hughes
Continuity mistake: Chapter 2: Freezing Torture. When the avalanche falls on the group, they are on a slope but they were on flat ground the shots before. You can also see that the people are actually dummies because they don't move.