Wrong Road - S2-E22
Revealing mistake: Wires to power the lamps are very visible on Gordon's and Edward's buffers, and bulbs are also sticking out from both their lamps.
Wrong Road - S2-E22
Revealing mistake: When Edward crosses the viaduct, the last coach of his train does not have lighting.
Wrong Road - S2-E22
Character mistake: The narrator refers to the brake coach as the guard's van.
Visible crew/equipment: The reflection of a crew member's face is visible in the window of Edward's cab when his driver cheers him on.
Thomas and the Missing Christmas Tree - S2-E26
Visible crew/equipment: In the scene of Donald and Douglas going out of the yard, a camera tripod can be seen in the top left corner.
Thomas and the Missing Christmas Tree - S2-E26
Other mistake: In the shot of Donald, (or Douglas) Gordon and Henry, Donald has Edward's face.
Answer: Breakdown trains help the engines back on track.