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Revealing mistake: In a close up of Stepney at the beginning, his lamp iron has a burn mark.
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Revealing mistake: When Stepney is returning home through the fog, the source to power his lamp is visible.
Visible crew/equipment: When Stepney puffs through the fog after dropping off the stone loads, studio equipment can be seen in the top left corner of the screen.
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.