Deliberate mistake: In the scene where Helen snags a ride on one of the rail cars (grabs it with her hands then does her Tarzan imitation), one of the support beams for the track magically disappears to give her more space to grab the car. The camera doesn't cut, or even change position- it just pans, all in one shot. When she looks forward at the track, there's one beam a short distance in front of her, and one beyond that. She turns to see a rail car approaching, and when the camera pans back to see her grab the car, the distance to the next support beam has been doubled- the first beam disappeared.
xx:xx:xxChris Moyer Grice