Thomas and the Billboard - S12-E1
Revealing mistake: At the beginning of the episode, Henry has Gordon's face.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: When Stanley shunts Thomas into the yard, Thomas is eyeless.
Thomas Puts the Brakes On - S12-E17
Revealing mistake: In the very last shot of the episode, Thomas and Stanley are faceless.
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.