Other mistake: When the K1 Robot breaks out of Kettlewells factory in part 2 or 3, it trips up.
Revenge of the Cybermen - S12-E5
Other mistake: Shortly after the Doctor makes his speech to the Cybermen about how pathetic they are, you can see a Cyberman's head wobble.
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