When Welsh is absently monologuing about the Musical Ride, Ray is seen fingering a pencil in both hands. Cut to a close-up of Diefenbaker, and Ray's right hand is hanging empty at his side.
When we initially see the train signal operator's off road truck, Diefenbaker is on the back seat. When the truck crosses the stream and enters particularly rough terrain, there is Diefenbaker in the back seat.
On Inspector Thatcher's Scarlett tunic she's wearing service stars and weapons qualification badges. RCMP members who hold the rank of Inspector and above do not wear service stars or any other qualification badges.
Fraser Sr. and Frobisher, while trying to figure out how to stop the runaway train, note a handle marked 'ENGINE BRAKE.' The handle is actually the train brake and is in the full application position. Below it is the engine brake, which is also fully applied; there is no point to the 'bypassing' wires since train brakes are entirely pneumatic and cannot be 'bypassed' electrically.
After diverting the train onto the spur track, Bolt's gang uses a remotely controlled high-rail truck to fool the FBI into thinking the train is still on the main line. High-rail trucks can't be monitored digitally since they are too light to activate track circuits. Even train dispatchers can only monitor their movements through radio contact with the operator.
When Fraser begins singing and playing the guitar on the train, his fingers don't move on the frets the chords change.
The uranium train doesn't have a buffer car between the locomotive and the loaded uranium car, as required by federal regulations. Also, the 'uranium' car itself is obviously a rail-mounted electrical transformer with radioactive markings painted on.
When Ray is warning the Mounties about the impending collision with the nuclear waste train, the engine control panel is visible behind him. The isolation switch is in the "Start/Stop/Isolate" position; it should be in "Run" if the engine is producing power to pull the train.
There is no way Frobisher could have lined a rail switch by simply firing a rifle at it. Even if the bullet hit the switch target with sufficient force to move the points (quite unlikely), the keeper on the switch mechanism would have to be released and the hand lever lifted manually before the points could be thrown.
Today's locomotives have a "deadman" alerter device that automatically applies the brakes if no controls have been operated for a short time; the device can only be disabled when the locomotive is not running. However, this train's cab is unattended for almost half the episode, yet the device never kicks in. (The "runaway train" argument is meaningless since that term largely applies to long, heavy freight trains that have lost control on a descending grade.)