Plot hole: The Doctor and Romana comment on a recording which has finished playing before they have entered the room. Not only that, but all the other characters behave as if the Doctor and Romana had seen this recording.
Doctor Who (1963)
1 plot hole in season 18 - chronological order
Other mistake: The Brigadier says UNIT HQ is 'a Top Secret establishment'. It is, in fact, so secret that it has a large sign outside informing the world not only of its function, but also the name of the commanding officer.
Castrovalva - S19-E1
The Doctor: That's the trouble with regeneration, you never quite know what you're going to get. (00:12:15)
Trivia: This Doctor Who story was originally scripted and produced as a four-episode story, but, just two weeks before transmission, upon viewing the story, co-creators Sydney Newman and Donald Wilson felt that the final two episodes (Episode 3, 'Crisis'; and Episode 4, 'The Urge to Live') should be combined into a single episode. The new 'condensed' episode incorporated the opening titles of 'Crisis' with the closing credits of 'The Urge to Live'.
Earthshock - S19-E6
Question: In Earthshock, season 19, at the end of episode 3, the Cyber Leader views his troops marching down the corridor. Each column is headed by a Cyber Leader. Is this a mistake, or is there more than one Cyber Leader allowed per army?
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