Visible crew/equipment: When Bill and Ben pass a station, you can see a bit of studio equipment at the top of the screen. (Visible in HD full screen version).
Continuity mistake: When Bill and Ben notice their trucks are gone, there are guards in front of them, two shots later, there is no sign of the guards.
Visible crew/equipment: When Duck is being pulled out by Thomas, from the shot inside the barber shop, a camera and other studio equipment is visible behind Duck.
Visible crew/equipment: When Bill and Ben go by a level crossing, the top of the set is visible.
Wrong Road - S2-E22
Character mistake: The narrator refers to the brake coach as the guard's van.
Percy Takes the Plunge - S2-E11
Deliberate mistake: When Percy is being loaded onto the flatbed, Diesel appears, but he is not introduced until "Pop Goes the Diesel" (episode after this). This is likely because "Pop Goes the Diesel" was produced before this episode.
Suggested correction: There is nothing in the show suggesting that the episodes are shown in chronological order.