Other mistake: Chapter 2: Freezing Torture. When a Ming ship launches the first bomb at Flash and his friends, you can see somebody walking or skiing toward the explosion. The problem is that they are not moving. It may be footage from another film.
Flash Gordon Conquers the Universe (1940)
1 other 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.