Revealing mistake: In the extended version of the film during the buffalo hunt, there is a shot of a buffalo making a turn and in the distant horizon, you can briefly see a modern radio tower on top of a hill.
Revealing mistake: At the end, when the train destroys the time machine, right at the moment when it hits you can see a small explosion, which was used to trigger the destruction of the time machine. (01:43:03)
Revealing mistake: When Marsten's men are forcing Aborigines off a cliff, Quigley shoots one man who falls over the edge with his horse. Just as the horse and rider fall over, you can briefly see the rigging used to flip the mechanical horse over the edge.