Several times the number of attacking enemy spaceships varies from shot to shot.
When Sandy and Joe descend the ladder, Sandy starts first but Joe reaches the bottom first.
When the alien ship abducts the Star Talk research building, it is held in a "bubble" attached to the bottom of the ship. But when the ship prepares to land (on its belly), the building and bubble have disappeared.
Smoke from an explosion rises in the air and goes behind the twin moons of the alien planet. Obviously the moons were painted on a sheet of glass set in front of the camera.
When the last enemy ship rams the space station, the explosion clearly illuminates the station's suspending wires.
When enemy spaceship #6 is destroyed, the explosion accidentally knocks the ship in front off one of its wires, and we see it dangling. A shortened version of this shot is also used when ship #3 explodes.
Only in the scene where the robot provides cubes to Joe, Sandy, and Ben from its side compartments, the compartment covers have trouble staying shut.
Whilst flying through space, 'space' has the shadow of the window frame upon it, revealing it to be a rolling painted backdrop.
The "24 hour" clock on the wall is numbered from 13 to 24 which makes it impossible to know if the time on it is AM or PM. It should have been numbered evenly spaced from 1 to 24.