Plot hole: When Duck and Diesel leave the shed, Diesel follows Duck instantly, but the tracks they are on both lead to the turntable. As they are on different tracks to each other, it would be impossible for Diesel to follow Duck that quickly as the turntable could only be set to one track at a time.
Visible crew/equipment: In the restored version, when Bill and Ben leave Brendam Docks, the twins do not disappear. They just stop right at the top of the screen. The end of the set can be seen in a still from the episode: also, two hands can be seen pulling them backwards with string.