Visible crew/equipment: In episode four, the Dalek chasing the heroes up the ventilator shaft is supported by strings.
Revealing mistake: Watch the Mandrells closely, especially in the later parts of the story: one of them seems, at one point, to have forgotten to zip up the back of his costume.
Continuity mistake: The amount of dirt on the Doctor's face changes between the Bath House and the exterior filming.
Audio problem: In episode 2, the Kandyman's microphone picks up quite a bit of the Doctor's dialogue by accident.
Visible crew/equipment: In episode one, when Ian is first seen inside the pyramid, someone stumbles through the background. Some have claimed this is Barbara, but it happens too fast to tell.
Plot hole: Oscar really does keep a clean restaurant. Even after Shockeye has stabbed him with a knife, the knife is clean, with no unsightly blood to be seen.
Attack of the Cybermen - S22-E1
Revealing mistake: When Lytton stabs the Cybercontroller, some of the Cybercontroller's 'blood' gets splashed on the camera. (The 'blood' is green-dyed water spraying from the Cybercontroller's arm.).
Revealing mistake: In episode one, a wall wobbles as Benton hammers a nail into it.
Plot hole: Why doesn't Lowe simply shoot Leela the second her back is turned? Moreover, why does he take them to get medical help? It's made clear that the virus has everything it needs on Titan.
Earthshock - S19-E6
Plot hole: The freighter traveling back in time makes no sense. According to Adric, the Cybermen's computer is responsible, yet the Cybermen possess no such technology; their machine's task was simply to navigate the freighter towards Earth. The idea that time travel could happen by accident is also absurd. (01:30:05)
Remembrance of the Daleks - S25-E1
Continuity mistake: After the Special Weapons Dalek blows up the gate to Ratcliffe's warehouse, you can see that some of The Daleks were slightly damaged by the explosion. In all the following shots, they have been repaired.
Revealing mistake: When Ace is being attacked by the Haemovores, she strikes one of them on the head, causing its mask to go up and revealing part of the actor's neck.
Factual error: In 1638, a mathematician calculates that the asteroid will return in 350 years time, on the 23rd of November 1988. But in 1752, Britain's calendar was moved forward 11 days so that it matched with that of the Vatican. This means the asteroid would return on 4th December, so everything that is supposed to happen in this story after 1752 is 11 days out.
Factual error: There are currently well over 700 different native Australian languages, and undoubtedly many more have been extinct for centuries. The chances of a 20th Century European-Australian such as Tegan being able to understand a native Australian language from around 35,000 years ago are so astronomical it is beyond belief.
Earthshock - S19-E6
Factual error: The Cybermen sets four explosive charges around the outside of the door, yet only the middle part of the door is damaged...
Revealing mistake: In episode 3, when the second Doctor, the Brigadier and Benton emerge from the TARDIS, the doors are left completely open with the camera looking straight into them for a long time, revealing not only the emptiness of the police box shell, but also that there's a pair of secret doors on the opposite side to the entrance doors. These 'secret doors' come in handy during episode 4, allowing seven people to come out of the police box in the final confrontation with Omega. (Well, it is stated time and again that the TARDIS is "bigger on the inside than the outside". Now we know how that happens...).
Revealing mistake: When the crack in the wall breaks open, the wall wobbles rather obviously.
Revealing mistake: In the UNIT tracking room, there is a flimsy railing behind the radar operators that Chinn knocks as Yates leads him off to the "direct" phone line, causing it to wobble badly. The Doctor then deals the railing another blow as he comes up to look at the console.
Genesis of the Daleks - S12-E4
Continuity mistake: In episode 6, when the lead Dalek is saying 'Pity? I have no understanding of the word' the lights on the top of its dome stop working. They start working again in the following shot. (00:21:00)
Revealing mistake: In episode 6, when the Brigade Leader shoots the Primord Stahlmann, he falls down but no bullet holes are made in his costume. Thanks to Producer Barry Letts for spotting this one on the DVD commentary. (00:17:00)
Answer: TARDISes are generally available for properly authorised use on Gallifrey; they're not usually assigned to a particular Timelord on a long-term basis. The Doctor stole his when he left his homeworld.
Tailkinker ★