Visible crew/equipment: In episode four, when Ian and the Doctor descend the stairs into Frankenstein's lab, you can see a boom operator and mic behind Ian, at the left side of the screen.
Revenge of the Cybermen - S12-E5
Plot hole: Sarah is transmatted down to Voga after being injected with alien poison by a Cybermat. According to the Doctor, the transmat will recognise Sarah's human molecules and separate and reject the (non-human) poison molecules. As clothing fabrics tend to made of non-human molecules, how come Sarah and Harry didn't arrive on Voga stark naked?
Continuity mistake: When Uvanov captures Leela he says she has killed three people, but he only knows Chub and Cass are dead. Then Poul tells him about Kerril.
Revealing mistake: One of the stones wobbles when a crow lands on it in episode one.
Underworld - S15-E5
Revealing mistake: The pacifier devise is obviously a stage lamp.
The Armageddon Factor - S16-E6
Plot hole: In episode four, Merak expounds on how only the Doctor and Romana can get into the TARDIS, despite the fact that he shouldn't even know what the TARDIS is. His insight continues in episode six, where he talks knowledgeably of the sixth segment of the Key to Time, despite having been told nothing about it.
Visible crew/equipment: In episode one, when Dai Evans is on the telephone in the mine, an arm of a crew member appears to the bottom right of the screen, giving the actor his cue to speak.
Revealing mistake: In episode two, when Leela and Mandrell are arguing about raiding the Correction Center, the camera bumps against something.
Continuity mistake: In the opening TARDIS scene, after the TARDIS lurches from the time scanner, the Doctor's hat rack can be seen standing upright. Then Leela picks it up in the next scene.
Continuity mistake: When the twins start to play equations they are both facing towards us. If they were to face each other, their legs would be touching each other. During the game we again see them at this distance apart. But the third time we see them (as they finish), they have moved at least a metre apart, making it possible for them to face each other comfortably.
The Talons of Weng-Chiang - S14-E6
Revealing mistake: At various points in the series, Mr. Sin is obviously a dummy and not an actor. But the most obvious is during the last fight when Sin jumps the Doctor. After a struggle, cut to a forward angle and the Doctor grabs and throws an obvious dummy to the ground.
Factual error: The Doctor meets Jamie at a time after the Battle of Culloden. But here Jamie says he met him in 1745. Culloden took place in 1746.
Genesis of the Daleks - S12-E4
Continuity mistake: When the Doctor drops the time ring, it lands very close to the wall. When he picks it up later, however, it's in the middle of the corridor. (00:09:40)
Visible crew/equipment: Near the end of episode five as The Daleks plan their attack, a BBC camera can be seen in the background on the right. (00:21:20)
Revealing mistake: When the Doctor is trying to unlock Uvanov's cabin door, Leela goes to join him and grabs the edge of the metal railing, which bends badly and then goes back to its original shape.
Revenge of the Cybermen - S12-E5
Other mistake: Shortly after the Doctor makes his speech to the Cybermen about how pathetic they are, you can see a Cyberman's head wobble.
Revenge of the Cybermen - S12-E5
Continuity mistake: For a supposedly emotionless creature, the Cyberleader is easily provoked to a fit of rage, including throwing the Doctor around the Beacon.
The Daleks - S1-E2
Plot hole: Why does The Daleks' prison have beds? The Daleks don't need them and clearly state that they have no idea what the Thals look like, speculating that they are "horribly mutated".
The Monster of Peladon - S11-E4
Visible crew/equipment: When Azaxyr is setting his ambush for the miners in episode six, a studio light can be seen through a gap in the wall.
Plot hole: 10,000 Daleks sounds impressive but it wouldn't be enough to invade a planet, let alone an entire galaxy.
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 ★