A train in England now or in the 40s would not have a 'conductor'. British trains are driven by a "driver" and the staff member who liaises with the passengers is the "guard".
That is true, but the Orient Express doesn't begin in Britain.
If the crown prince's father is the King, then he should have been addressed by Henry as "Your Majesty", not "Your Highness", which is only appropriate for princes.
The scene where Henry asks for a tube to pump the stomach:
Sgt. Mike goes into the kitchen and pulls out the spray faucet attachment and hose at the sink. Such an action would have water flooding the floor.
Prior to dying from "lung cancer", Armen Aronov is feeding bread to pigeons. When the camera shot shifts to different view points, the plastic bag with the bread next to Aronov disappears and reappears.
When Lucas scans the stomach contents he uses a laser temperature probe yet it makes the sound of a Geiger counter.
Henry threatens to tell the FBI about the Puran's finances in order to get him to talk. As an agent of the Consulate, Puran has Diplomatic Immunity and would have known Henry was bluffing.