Factual error: In the subplot on earth, the heroes' family members are trying to outrun the falling moon's gravity that's sucking everything into the air. So, naturally they duck into a barn, because, of course, gravity can't affect you behind a wall. And sure enough, behind the wall, they're suddenly safe.
Factual error: In one scene, Winifred asks Gilbert who Trask is and Gilbert replies that Trask is the "mayor", to which Winifred just acknowledges. However, the office of mayor was not created in Massachusetts until 1823, which is 130 years after they were hanged, so given the witch's lack of knowledge of the modern day, she would have likely not known what Gilbert meant.