Visible crew/equipment: When Mimi is escaping from the castle and swinging on the drain pipes, the wire holding the whole lot up is visible. (00:29:10)
Visible crew/equipment: After Mimi has cut off the magnetic button and launched it away with James' braces there is a shot of the exploding grouse and the wires making it fly are visible. (00:31:00)
Visible crew/equipment: In the shot where the 'Dual Carriageway' sign is seen and the cars drive over the camera, the man driving the milk-float that is meant to be being controlled by radio is visible. (00:35:25)
Visible crew/equipment: When James is visited in his chambers in the Scottish Castle by the "widow", someone is in the mirror as she enters. When she moves forward, and the film cuts back to her from James, the person is no longer in the mirror, even though the angle is the same.
Answer: Given that this is a comedy, the thinking was probably "Well, we'll just blow up your retirement so you've got no choice but to come out of it."
Captain Defenestrator