Revealing mistake: The rails to the buffers are broken as Toad leaves the siding.
Revealing mistake: When Toad switches lines to avoid Gordon, the track ends in bushes.
Revealing mistake: When Gordon puffs into the ditch his face looks wonky and wires are visibly attached to his cab.
James and the Trouble with Trees - S5-E5
Revealing mistake: In the end of the episode, you can see James doesn't have his face fitted on correctly, as the gap between it and his eyes appears to be exposed.
A Bad Day for Sir Handel - S4-E6
Revealing mistake: When Sir Handel derails, you can see a small rod sticking up out of the ground from the tracks.
Revealing mistake: When Samson crosses the Vicarstown Bridge, there is no shadow effect on his face.
Revealing mistake: When Gordon falls into the ditch, wires under his cab are visible.
Revealing mistake: The old engine's model, who fell off the bridge, was actually Skarloey's, as some red paint can be seen.
Revealing mistake: In a shot of Duck at the smelter's, a hole is visible on his running board.
Revealing mistake: When Toby tells the Fat Controller about the broken windmill, his driver's head appears to have been digitally added.
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.
Revealing mistake: In a close up of Stepney at the beginning, his lamp iron has a burn mark.
Revealing mistake: When Stepney is returning home through the fog, the source to power his lamp is visible.
Revealing mistake: The end of the set is visible in one shot at the quarry.
Revealing mistake: Duck's footplate clips through the platform at Knapford at the beginning.
Revealing mistake: Before James collides with the tar tankers, he is already covered in tar before he actually hits them.
Revealing mistake: When Thomas collects Rocky, the points are set against him. This also happens when Percy enters the siding.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: When Stanley shunts Thomas into the yard, Thomas is eyeless.
Fergus Breaks the Rules - S7-E18
Revealing mistake: A wire is under Fergus when he arrives at the smelter's.
Answer: Butch the breakdown truck must have pulled Gordon's tender all the way up the rails so the breakdown train can reach it and also Butch helped to get Gordon close to the winch.