At the beginning of the movie, when the bad guys get to town and start walking around, within a few minutes it goes from night to bright sunny day and back to night.
When Reb Carlton (Zachary Scott) is supposedly pinned to a tree by an arrow, the arrow can be seen moving with Reb's breathing, showing it was just strapped to his chest.
The stage station has a corral with an inclined stock ramp, an item that did not exist before the need to load animals on to trucks.
Abby's (Yvonne De Carlo's) hair and costume were not of the Western era.