Other mistake: Whenever the gang are in their clubroom (inside the bus), in some scenes the walls wobble when the door is opened or closed.
Here Come the Double Deckers (1970)
1 other mistake in show generally - chronological order
Starring: Peter Firth, Brinsley Forde, Gillian Bailey, Michael Audreson
Audio problem: Billie says her line "he needs a new image" without moving her lips.