Resurrection of the Daleks - S21-E4
Audio problem: Davros' lips don't move when he says, "Now for The Daleks," just before he releases the Dalek-killing virus.
Resurrection of the Daleks - S21-E4
Revealing mistake: When Lytton and his men approach the self-destruct chamber in episode three, the door is closed in front of them. It wobbles as it closes.
Resurrection of the Daleks - S21-E4
Revealing mistake: When the Doctor is shooting the Dalek creature hidden under the coat, he is obviously using blanks because when you see the coat there are no bullet holes in it.
Resurrection of the Daleks - S21-E4
Other mistake: When the Doctor's mind is scanned, we see his previous incarnations and companions, but Leela is not shown. Katarina is represented by a black and white photograph.
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 ★