The Sad Story of Henry - S1-E3
Audio problem: When James is about to puff away from Henry's Tunnel, if you listen closely, James is heard puffing before he has even left. (00:10:00)
The Sad Story of Henry - S1-E3
Revealing mistake: When the passengers try to pull Henry out of the tunnel, they have putty on their feet. Sir Topham Hatt's hand is also purple.
Answer: Breakdown trains help the engines back on track.