Visible crew/equipment: In episode three, when the Doctor enters the Pavilion of the Summer Winds and shuts the door, the door slowly swings open again. A hand then appears from behind the set wall and pulls the door closed.
Revealing mistake: Zadek claims the water door into Castle Gracht is a foot thick. But it is obvious when the Doctor crawls through that it is paper thin.
Revealing mistake: When K-9 is cutting through the wall of the hut, the cut overtakes his laser at one point.
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