Although the two men stay in their private berth and are oblivious to what is going on as the decoupled passenger car rolls down the side track into Gudavia, multiple exterior shots of the rolling car show different sets of windows either open or closed from shot-to-shot, although there was no one else on the car to open or close the windows.
In the opening sequence a train is shown approaching bridge, then an interior of the train with the two main characters then the train approaching the same bridge again.
As the single train carriage comes to a halt there is the sound of brakes being applied. However, with only two passengers on board the carriage there were no rail staff travelling in the carriage to apply any brakes.
When the two boys switch the points there is no reason for them to do this as they couldn't know there was a decoupled coach following the train, as it was caused by mechanical failure and was not planned.
When Mike Wilson rolls down the hill, it is an obvious stuntman, slimmer and darker-haired than Paul Douglas.
During the sequence where Paul Douglas is trapped in the heat chamber the villain (Walter Rilla) can be heard making snide comments, but his mouth isn't moving.