Other mistake: In the Family Jr. airing, Davey Moore is not credited for writing the episode; Andrew Brenner is. This mistake was fixed in the UK airing.
Audio problem: After Rex is hoisted back on the rails, Mike has Rex's whistle sound.
Springtime for Diesel - S21-E1
Audio problem: Trevor has Stanley's whistle sound when he crosses the level crossing.
Answer: Breakdown trains help the engines back on track.