Revealing mistake: In the last part, the giant robot steps on a soldier. There are several things wrong with this scene. 1) You can see the matte halo around the robot's foot. 2) The robot does not leave a footprint. And 3), after the soldier gets squashed, his arm is visible waving over the robot's foot.
Audio problem: In part 4, when the cybermen are outside the moonbase controlling the workers, the mouth of the radio operator does not move when he is speaking to them. Furthermore, a few of the cybermen's mouths outside the moonbase are stuck open when they have no dialogue.
Visible crew/equipment: (Part 3) After Omega has revealed himself to the Third Doctor, Jo, and Dr. Tyler, when he begins to speak privately to the Doctor the camera casts a shadow on Omega's body. Then after Omega turns around the boom mic dips into view at the top of the screen. And when Omega starts walking forward, the shadow of equipment (presumably the boom and mic) can be seen moving on the far wall, near the lower left of the screen.
Visible crew/equipment: In Episode 2 when Marc Cory and the other Ambassador are talking, a figure who appears to be wearing Space Security Uniform (and this isn't Nicholas Courtney) and a stage hand walk by, and you can also see the end of the set.
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