Visible crew/equipment: The arm of the actual carriage driver is visible poking through the back of the carriage, slapping the horse and signaling it when to stop/proceed with a second set of reins, showing the actor in the carriage was not controlling the horse at all.
Factual error: At the mint, Arte hides in a broom closet. He carries nothing in (nor did he hide anything in there beforehand), yet he emerges later in an "old man" disguise, wearing a wig, hat, mustache, false nose, glasses and janitor costume. Magic closet?
Factual error: The small round table in West's railcar parlor has a flip-over top, with secret maps hidden on the underside. The wine decanter and glasses all stay attached when it flips. But impossibly, when West turns the tabletop back over at the end, there's a full cup of coffee sitting on it.
Revealing mistake: West and Gordon burn a perfect circle (unlikely in and of itself) in the metal floor in order to break into the dungeon below. West punches the circle out with his fist, then grasps what should be white-hot edges with his bare hands before jumping through the opening. Even if wood it would still be too hot to touch.
Continuity mistake: West describes to Artie his movements through the fortress using a model of the structure sitting on a table with a green table cloth and gold trim. West's left hand is resting on the table, as is a clear glass dish, as well. Close ups show the model close to the edge where the dish was and West's left hand on his thigh.