Other mistake: At the start Gordon's buffers are crooked.
Revealing mistake: When the boys sing, the camera shakes.
Revealing mistake: When Gordon is being pulled from the pond, in the close up scene of Gordon reversing up the sleeper bed, the front of his buffer beam/running board catches on the upright stake to the right hand side of the worker figure, pulling it back before it rights itself. (easier to see on widescreen version). (00:04:10)
Revealing mistake: When Gordon puffs into the ditch his face looks wonky and wires are visibly attached to his cab.
Revealing mistake: When Gordon falls into the ditch, wires under his cab are visible.
Answer: He was in the water.