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
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: In 'The Five Doctors', three separate Cyberleaders are definitely used. So it's likely that Cyberleaders are like unit commanders, of which a fair-sized army might have several.
Daria Sigma