Audio problem: In the scene where Chitty Chitty Bang Bang is passing the train you can see a continuous trail of smoke issuing from the train. It is exiting from the train's whistle, meaning that there should be a continuous high pitched whistling noise, yet there is no such thing.
Audio problem: When Sid James comes out of the building, in the scene at the end with the big fight, a man comes up to him and Sid asks, "You wish to see me?" Just before this, you see him mouth the words to that line.