Continuity mistake: Despite Henry's issue from "Coal" in Season 1 being resolved after the crash in "The Flying Kipper", also in Season 1, Henry needed special coal again from "Thomas and the Magic Railroad" until Season 16.
Continuity mistake: Bulgy was converted into a vegetable stand in "Bulgy Rides Again." But from "Excellent Emily" onward, he is a passenger bus again.
Continuity mistake: Throughout Season 4, Henry is painted in two different shades of green.
Answer: Breakdown trains help the engines back on track.