Other mistake: When Quaid goes through the x-ray machine the first time, the person behind the man with the dog isn't shown to be carrying anything (there's no purple object shown). But then later the purple object is seen.Bishop73
Other mistake: After Arnold kills Harry and his gang at the beginning, how did that blood splatter get on the wall behind him to his right? He shot the henchman standing in that position from the back and the other who was shot was shot standing to the left side of the wall. So there is no explanation why the splatter is there.