Revealing mistake: When Cabal and Passworthy look upon the distant searchlights from their doorstep, it's plain that the "beams" of light are really just solid dowel rods being swung about.
Visible crew/equipment: When John Cabal has his aerial dogfight early in the war, there's an over-the-shoulder shot of him in the open cockpit of his biplane. As the plane maneuvers through the air, the shadow of the camera, mounted to the fuselage, passes plainly into view.