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: Guy flushes the toilet as he walks through the bathroom. The toilet is actually empty and the sound is an over-dub because there is no resistance on the handle when he pushes it down. Had an old toilet like that actually been full you would see the resistance in the lever as the flapper inside rises. (00:04:45)