Eighty-three minutes into the film, a bullet hole suddenly appears on a steel cable car right behind Charlie as she ducks bullets with Grant. Charlie looks behind her, apparently reacting to the sound of the bullet hitting the car - but there is no sound whatsoever.
When the train collides with the water tower, it is on dual gauge track, with three rails. When Grant gets up to walk along the track, it is now single gauge with only two rails.
When the gang returns to their hideout after robbing the train, Latigo holds up the bottle of whiskey he took from the train. The card players all come to the bar for a glass. When the bottle is carried to the table it is still full.
Grant McLaine finds the hideout much too easily.
At the old mill during the shootout you can clearly see an airplane strip in the sky.