Goofs

Willie meets Gary for the first time with his gun drawn on him. Seconds later a gunman charges Willie and Willie has to draw his gun to shoot the man down. While this appears to be the case, you can see the motion of Willie holstering the gun as Gary stands up and answers 'Yes, sir.' followed immediately by the attack from the right by the Zavala assassin, forcing Willie to draw again.

When Barbarosa and Karl start to climb the cliff, it is a cliff that rises in front of level ground. But as they climb, there is now a river at the base of the cliff and that river have carved a canyon, with a cliff on either side. When Karl goes back down the cliff to get the money he had earlier thrown down, he falls into the river. But when he climbs out of the river, there is now flat ground on one side of the river where there had earlier been a cliff (and on what had once been the far side of the canyon).

There is no tractor pulling something as the horse racers round the home stretch. It is clearly a wagon pulled by horses. They actually did a good job of having it in the background in the three quick shots that showed the racers.

In the scene where the race contestants approach the finish line where Willie and Gary have stopped to watch, just as the riders round the curve to the finish, you can see a farm tractor pulling something behind the racers.