Factual error: The evil man request 100,000 pieces of gold for ransom. Each gold piece looks to be about 10 ounces, and 100,000 of those would make the entire thing weigh about 31 tons, but 2 guys are carrying it around in a little chest throughout the movie.
Continuity mistake: In the desert, when Roy is buried alive, Jackie walks up and casts a shadow over his face. In the next shot, the shadow is facing a different direction. It continually changes throughout this scene.
Continuity mistake: At the end of the hanging scene when the horses and wagon charge the gallows, the wagon hits the structure, the sheriff falls, you can see the horse break free from the wagon, leaving it under the fallen gallows. The next scene the horses are back attached to the wagon again.
Continuity mistake: When Jackie goes into the tent (at the coal mine) to talk to the Princess, it is broad day-light. When he comes out (three minutes later) it is pitch black out side.
Revealing mistake: This mistake occurs in the beginning of the film where the bandits rob the train. When Jackie is standing on the coal (or was it wood?) car you can see the train is passing a modern sign (you can see it on the right).
Continuity mistake: Near the beginning of the film, when the three volunteers are kneeling and Jackie Chan comes up behind them, he also kneels down at a considerable distance behind them. The camera cuts to a different shot, then immediately back to the Imperial Guards, and now Chan is directly behind them.
Continuity mistake: When the camera is under the train in the beginning of the film you see only one carriage/wagon pass over the camera, but in fact it should be a train with several wagons.
Continuity mistake: When trying to escape from Roy's 'hideout', Roy doesn't have his hat with him. Later when he saves Chon in the Chinese encampment he has it. In this scene he says that he followed Chon so he wouldn't have had time to return for the hat. Also, returning to somewhere that he is well-known for frequenting would have been foolish considering there would probably be quite a few people out looking for then as they had just escaped being hung.
Continuity mistake: At the last part of the hanging scene when Roy falls into his casket, you can see that his hands aren't tied together when he falls in. But in the next shot, he's on his back with his hands still tied.
Visible crew/equipment: When they are breaking out of the jail cell, when he opens the door, there is a person that holds the door open.
Continuity mistake: When Jackie is fighting the bad guy at end at the top of the of bell tower, the bad guy bends his sword very badly. When they fall to the bottom and the bad guy picks his sword back up, it is perfectly straight again.
Factual error: Just before we see Roy O'Bannon's gang for the first time as they are preparing to rob a train, we see a shot of the train winding along track in a very picturesque valley. However, the tracks are paralleled by very modern telephone poles with several wires on them. If this was truly the old west, the poles would have had only a single wire on them for the telegraph service.
Continuity mistake: When Chan is planning to leave Roy and go it alone, he takes his hat off of his horse. The camera cuts to a shot from behind Chan, and the hat is now hanging behind his neck.
Revealing mistake: At the end, when Jackie is fighting the bad guy, he jumps up into a windowsill and then jumps down when the bad guy tries to hit him with a spear. If you look at the spear when it hits the wall, you can see that the spearhead is made of rubber because it bends when it touches the wall.
Continuity mistake: When Chon and Roy are on the gallows about to be hanged, there is a series of quick switches between shots of the gallows and shots of the girl's hands as she loads a rifle, cocks it, and raises the sight to take aim. However, those three shots (muzzle, cocking mechanism, and sight) are of three different firearms; none of which are the one she is eventually seen firing at the gallows.
Continuity mistake: When Chon attacks Roy for touching his ponytail, he has a cowboy hat on. During the attack, Chon's head goes out of sight for a second and then comes back in but his hat has disappeared. Also, right after that Chon says, "Never touch my cue," and he pulls his hat out of nowhere.