Revealing mistake: In episode 1 when the Doctor is checking the controls you can see the studio lights to the top left corner where the set doesn't completely connect.
Continuity mistake: Towards the end of episode 2 it's nighttime, but when Ian and the Doctor lure the Dalek over from the TARDIS, and when it falls, it's daylight.
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