The Moonbase - S4-E6
Audio problem: If you listen carefully to the soundtrack of part four of "The Moonbase", some 'chatter' and 'feedback' from the floor manager's headphones can be heard. (At the time this particular episode was recorded, there was just a one-week gap between recording Doctor Who and transmission, so there was no time available to re-record the episode, and this mistake had to be left in).
The Moonbase - S4-E6
Revealing mistake: The doors and walls wobble badly as Jamie and Ben barricade the entrance to the medical unit.
The Moonbase - S4-E6
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.
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB