Factual error: In the scene where the people of Rejection/Perfection are preparing to fight the Dirt Dragons, Hereim loads the Punt Gun and puts a little gold piece in it (a percussion cap, containing a small amount of gunpowder used to set off the main charge in the barrel). He shoots at the Dragon when it pops up and misses. The next time he loads the gun, he does not replace the percussion cap (which can only be used once), yet he is still able to fire the gun with no problem and kill the Dirt Dragon.
Factual error: In the muling station, Juan is at the telegraph when a Graboid comes up from underneath him. As he is flung up into the air, he 'hangs' there for just enough time to disprove the law of gravity. Also when the Graboid breaks through the floor, it is just behind Juan, which would have sent him forward (over the telegraph) - yet he is thrown backward. (00:57:30)
Factual error: Lu Wan Chang is wearing a denim "jean" skirt with slits in the movie. Though denim or jean pants have been around for 10 years in the movie's setting, jean skirts were not introduced until the 1960s. The fit of the shirt and the slits also would have been inconsistent with modest dress of the women of that time.