Continuity mistake: In the scary door, the hay stack on the barn it diagonal, but when the aliens are attacking, the hay stack is vertical. (00:13:30)
Continuity mistake: During this scene, the female lead, Freya, is being attacked by the Moorwen youngster in order to eat her. When above her, the Moorwen's saliva is dripping onto her face, cut away to the monster, as it hears the main characters coming to her rescue. Cut back to Freya and there is none of the saliva on her face, another cut back to the creature and a final cut back to Freya, her face is now covered in saliva again. (01:27:30)
Revealing mistake: The El Camino that is going over the cliff, which has just been shot in the tailgate with a 50 caliber rifle, has no tailgate damage. Also at the same time stamp, when the El Camino is upside down, it is obvious there is no transmission or drive shaft in the car. They even show you this with a close-up. (00:46:20)
Character mistake: The professor identifies the "sea monsters" as plesiosaurs from the Pleistocene. Plesiosaurs became extinct at the end of the age of dinosaurs, nearly 60 million years before the Pleistocene. Of course, the Loch Ness Monster might be an exception.
Factual error: One of the women in the group picks up a piece of calcite (Iceland Spar variety). It is obviously calcite because of the very obvious rhombohedral cleavage and other visual indicators. The sample is later identified as ringwoodite. Ringwoodite is cubic with no reported cleavage. Even if it did exhibit cleavage, it would not be rhombodedral.