During the final shootout the background lighting on the closeups and master shots of John Ireland do not match.
When Jesse James goes to straighten the picture on his wall, the opening shot shows the picture slanting down to the right. When the camera angle changes, the picture is slanting up to the right. When the film cuts back to the first angle, the picture is slanting down to the right again.
After Ford has five bills tossed in his face, they fall to the ground, scattered about. One behind him near his boot heel, and another near the chair off to his right, and he picks up the two closest to him. As the camera switches to a closer view, the bills have moved and three a laid out right in front of him.
When Jesse's wife serves bread at dinner, the bread presented has obviously been sliced by a modern bread-slicing machine. Bread-slicing machines were not introduced until 1928.