Plot holes

Given the family's fear of discovery, why the would light fires at night or in the early evening when they would be seen from many more miles away than in the daytime is never explained.

Character error

On more than one occasion in the film, a lead character uses gasoline as fuel to start a fire, but then carelessly leaves the gas can in dangerously close proximity to the open flames as he lights his matches and starts the fire. In real life it would have been extremely likely that fumes from the gas can would have ignited, being so close to the open flames, and possibly caused serious injury or death to the lead character or others nearby.

Continuity

The pickup truck used in the film initially has the branding on the front grille worn away/blacked out. But when Paul later returns to his house with Will's family, the grille badge has mysteriously returned.