A character says Petty painted the mines on the beach sand colored, yet when the bomb squad dude is trying to disarm it, the mine is the same dark green color as the others.
After she gets Petty out of her car, Madsen pulls her hammerless gun and points it at Petty. Yet another gun cocking sound is heard, something that is impossible for a hammerless gun such as hers. Likewise, after Hauser shoots Petty and then threatens him with his gun, the gun cocking sound is heard. Hauser's gun having been fired was already cocked. It was likely the same hammerless gun he had used earlier, but either way it would be impossible for him to make the sound heard.
When confronting Petty on the beach, Hauser steps on a mine, yet the sand on top of it is undisturbed. Since Petty was in the process of planting another mine a few feet away, he had just planted the one Hauser stepped on. As such, it would be impossible for the sand to remain undisturbed. It is later revealed he painted the mines to blend in with the sand, but that was irrelevant since he still had to dig up the sand to plant the mine.