Continuity mistake: In episode three, the readout strip dangling from K-9's mouth shortens between when he shoots the infected crewman and shoot Leela.
Continuity mistake: When the Doctor shoots Stor with the De-Mat Gun, the flash starts on Stor's left-hand side, engulfs him, then jumps substantially to the right before whiting out the frame.
Continuity mistake: After shooting the two guards near the beginning of episode three, K-9's nose blaster retracts twice - one in close-up, once in medium shot.
Continuity mistake: When Palmerdale wakes Harker up and asks him if he can use the telegraph, Harker answers him, then asks him to repeat the question, then answers again.
Continuity mistake: Lowe's "frozen" makeup changes between when he emerges from the freezer and when Leela brings him a cup of coffee.
Continuity mistake: The Doctor has his scarf when he first meets with the Vardans. When he returns to the TARDIS, it is on the coat rack.
Continuity mistake: The TARDIS is missing its light the first time it's seen.
Underworld - S15-E5
Continuity mistake: When the Doctor races out of the R1C with the fission bombs in episode four, Leela follows, carrying a shield gun. She steps into the cave and is only holding her knife. Later, she has her shield gun back.
Continuity mistake: The Gatherer gleefully states that being on the roof is a fine of 500 talmars. Later, Cordo says it is 5 talmars.
Continuity mistake: The countdown clock in Marius' lab speeds up and slows down as needed for the plot.
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: In episode 4, Skinsale is murdered by the Rutan on the stairs right outside the crew room but later in the episode when the Doctor and Leela runs down the same stairs, Skinsale's body is not there.
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 ★