The Caves of Androzani - S21-E6
Revealing mistake: When Stotz cuts a hole in his ship's door, you can see that the inside of it is made of white polystyrene. They painted the outside of it but obviously forgot about the inside. Also listen to the sound it makes when Stotz punches the hole through - it sounds exactly like polystyrene.
The Caves of Androzani - S21-E6
Factual error: Sharaz Jek's monitor that displays the tunnels and his androids is inaccurate. The white blobs are, as we learn later, supposed to represent his androids. He tells the Doctor that the green area is held by the army, yet on the screen the green area is populated by androids, so they could not have had control.
The Caves of Androzani - S21-E6
Continuity mistake: When the Doctor and Peri first land on Androzani, mountains are seen in the background. They disappear when Peri picks up the silica. A couple of shots later, they're back. (This mistake was mentioned on the DVD commentary; the mountain effect was left out for financial reasons).
The Caves of Androzani - S21-E6
Revealing mistake: In the very first shot of Morgus' hand-held computer, it's obvious it's a TV remote. Look for the controls for contrast and tint.
Continuity mistake: After the Raston Warrior Robot has killed all the Cybermen, watch the dead Cyberman in the back right of the picture. His arm position changes as the robot teleports away.
The Dalek Invasion of Earth - S2-E2
Visible crew/equipment: When the Doctor and Ian are talking about the discs on The Daleks' backs, you can see a female crewmember behind the robomen, standing there and then walking off, and then another crewmember in a white shirt dart past the robomen.
Genesis of the Daleks - S12-E4
Deliberate mistake: Chief of Security Nyder wears an iron cross on his uniform which mysteriously disappears in episode 3 - apparently the producers felt it was too close a reference to Nazism so it was removed from the show. (Source: DVD commentary).
The Caves of Androzani - S21-E6
Continuity mistake: When the Doctor is climbing through the tunnel to the Queen bat, note the question mark on his lapel: the image is reversed.
Visible crew/equipment: Episode 5, while Zoe and Jamie are at the Weather Control Station, when they hear the Ice Warrior approaching they both hide, and the actor's T-mark is visible on the floor. (00:18:00)
Visible crew/equipment: (Episode 5) When Vicki is in the jungle she happens upon the TARDIS and bangs on the door begging to be let in. In the next shot we can see the boom pole/mic hovering in the background, then a hand appears which seems to guide the actress to head in that direction. (00:07:45)
Remembrance of the Daleks - S25-E1
Character mistake: The gate to I.M. Foreman's scrapyard reads "I.M. Forman."
Attack of the Cybermen - S22-E1
Visible crew/equipment: Just after the Cyber Leader orders that Flast be thrown out of the refrigerated room, one of the floor crew can be seen kneeling behind some crates. (01:20:50)
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 Slaar discovers the video link is operational and being viewed on Earth, in the closeups of Slaar we can see the edge of the reptilian mask and the actor's real human neck. (00:20:40)
Revealing mistake: Episode 6, while in the barn Von Weich asks Moor (played by David Troughton, son of Patrick, who plays The Doctor) to retrieve the monocle in his pocket. Then, when Von Weich continues with his plan, in his closeups we can see a vertical piece of mesh tape over the actor's right eye. (00:13:05)
Visible crew/equipment: (Episode 4) After Ian shudders from the apparition he continues to follow The Doctor down the hall, and the camera casts a shadow on Ian. Then, when The Doctor finds the stairs leading to the laboratory he tells Ian he must see what's on the table. Just as Ian states his displeasure at the thought, the boom mic (and its shadow) pops up into view at the bottom of the screen, in front of Ian. (00:05:15)
The Power of the Daleks - S4-E3
Deliberate mistake: During all the animated parts of "The Power of the Daleks" in numerous shots various illustrated character's such as The Doctor, Polly, and Ben have their buttons, pockets, patches, etc, flipped to the opposite side, sometimes even within the very same shot.
Revealing mistake: In episode 1 when the Doctor, Ian, Barbara, and Vicky leave the TARDIS, wheels are visible which move the prop around. There is also no back to the prop.
Continuity mistake: During the animated portions of Shada's missing scenes, in numerous shots an illustrated character's clothing (buttons, scarf, etc) become flipped, sometimes even within the same shot. Example: when The Doctor goes to the physics lab and meets Clare Keightley, note her buttons and The Doctor's scarf.
Continuity mistake: After Skagra demands the book from Professor Chronotis, as Skagra's sphere floats toward Chronotis he's wearing his eyeglasses, but then the Professor's eyeglasses vanish and reappear while his hands are raised.
Answer: It was never destroyed on-screen; it was intact at the end of the TV movie, and destroyed by the start of the 2005 series. It was destroyed in the novel "The Ancestor Cell," but in a completely different manner to what happened in the series.
DaveJB