Dragonfire - S24-E4
Revealing mistake: At several points in the story the 'huge heavy ice cliffs' get blown fractionally upward by people running past them, showing that they are made of very thin, very light plastic.
Dragonfire - S24-E4
Plot hole: At the end of episode 1, the 'cliffhanger' ending is that the Doctor climbs over some railings, and then, by looping his umbrella on the railing, he begins to climb down. He looks down and it seems to be a very long way down. This is resolved in episode 2 by having Glitz walk around and let the Doctor step on his shoulders. Not only is it silly, but because Glitz walked around, it also makes the previous 'cliffhanger ending' totally meaningless.
Chosen answer: The Master is insane. If he can't control the universe, he'd rather see it destroyed.
Captain Defenestrator