Visible crew/equipment: In several scenes there are rectangular arrays of studio lamps visible, reflected in the actors' space helmets.
Revealing mistake: Early in the film Gene Hackman tests a rocket-powered backpack outside the space station. He slowly spins sideways through a complete circle, but instead of each side of his body being lit up in turn as it's pointed towards the sun, the light stays constant throughout the maneuver, showing that the makers just took a photo of Hackman and rotated it.
Continuity mistake: Frankenstein buys a sprig of freesias as a buttonhole: two yellow flowers and a purple. The sprig immediately changes into two purple flowers and a yellow. When Frankenstein meets Mrs Brandt and they go into the drawing room, the flowers are two purples and a red with yellow centre. Once in the cellar to see Mr Brandt, the red goes, and a yellow is back with two purples. (00:57:45 - 01:03:55)
Revealing mistake: When the lift body first separates from the orbiter you can see the support wires for the orbiter hanging below (scene must have been filmed upside down).
Continuity mistake: When Carl lets his dog out of the bag, in the close-up there's a shadow on Rod Steiger's boot, and a shadow of something or someone standing between him and the camera: both are gone in the following shot, when the dog runs across the lawn (and 'knocks aside' the camera). (00:08:20)