Continuity mistake: In the very first scene of the story, Jo is holding a gun as she opens the TARDIS doors, but when they come into the console room, she has no gun and is using both hands to support the Doctor.
Plot hole: Professor Jones says they tried to borrow the cutting equipment a few weeks ago, but Mr. Stevens says it was yesterday. One of them must be wrong...
Revealing mistake: When Benton jumps over the maggots to get into the cave the Professor and Jo are hiding in, the jump causes the floor to move, giving away the fact that the floor is wood covered by a small amount of gravel.
Plot hole: Jo should know what the dematerialisation circuit looks like. She saw it in 'Terror of the Autons', 'The Three Doctors' and several other episodes.
Audio problem: When the companions are returning to Earth via the pillar of smoke, you can see and hear each person walk up the steps and then supposedly disappear. Unfortunately, you can then hear them walk down the other side of the steps..
Audio problem: About 10 minutes into episode 1, the sound of a pencil being dropped and rolling across the studio floor can be heard. (00:10:00 - 00:11:00)
Revealing mistake: In the finale, when Stevens is beating on the computer console, it moves around quite a bit, even thought it is supposed to be a strong and stationary object.
Revealing mistake: At the end of episode five, when James collapses against the wall, it wobbles under his weight.
Continuity mistake: In episode five, the Doctor escapes from Global during the day. When Yates is caught it's dark, but the next scene, on the slag heap, is in daylight again.
Other mistake: Near the end of episode 5, Stevens is reading out previous numbers of slave units and B.O.S.S is telling him the new ones. For New York, the previous figure was 7203 and the new figure 7580. However, for Moscow the previous figure was 10003 (ten thousand and three), and the new figure is 110098 (one hundred and ten thousand and ninety-eight), which is a big difference.
Continuity mistake: (End of Ep. 3 and start of Ep. 4) When The Third Doctor fights the dark side of Omega's mind, the rings that The Doctor wears on the pinky fingers of both hands switch to his ring fingers, then back again to his pinky fingers, between shots. Then as Omega chokes The Doctor, the ring on his right pinky vanishes between shots.
Deliberate mistake: When the Doctor and Benton are throwing fungus at the maggots in episode six, a shot of a chunk of fungus rolling down a hill between two maggots is repeated.
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.
Plot hole: 10,000 Daleks sounds impressive but it wouldn't be enough to invade a planet, let alone an entire galaxy.
Factual error: When the inside of an apple is exposed to the air for about fifteen minutes it oxidises and goes brown, but Jo's breakfast apple goes brown by the end of the scene. (This is assuming she wasn't deliberately eating a brown apple).
Character mistake: When the Doctor is saying the decimals of Pi to avoid falling under the control of BOSS. He gets it wrong; he says "3.1416..." When it's actually 3.141592.
Audio problem: In Part 3 when the Brigadier gets behind the sand pile with Arthur Ollis, the Brigadier asks him "Did you find a way in?" This is not Nicholas Courtney's voice for this one line. He speaks again right after that and it is his voice. (00:13:20)
Revealing mistake: Matte halos appear very frequently in this episode, particularly when descending into the mine shaft.
Revealing mistake: When Jo and the Doctor are rowing through the maggot lake, several times parts of the actor's arms disappear.
Visible crew/equipment: (Part 3) After Omega has revealed himself to The Third Doctor, Jo, and Dr. Tyler, when he begins to speak privately to The Doctor the camera casts a shadow on Omega's body. Then after Omega turns around the boom mic dips into view at the top of the screen. And when Omega starts walking forward, the shadow of equipment (presumably the boom and mic) is moving on the far wall, near the lower left of the screen. (00:03:10)
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