Go to the part where Rob Lowe is ready to jump onto the chase train to try and catch the runaway. Just before he drops down onto the engine, we can see both the numbers under the cab window and in the numberboards above the front window. Right there is the slip-up. The number under the cab has four numbers in it, as the numberboards over the windows show only a three digit number. Anyone who knows about trains knows that these two numbers should be the same number.