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 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: 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.
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 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.