Even in an institution for the criminally insane, patients have floors, lights, and beds. It is not legal to put someone in what can only be described as a cell with a dirty floor and nothing else.
(at around 51 mins) The name of the town in Long Island is Am/it/e/vil, not "A/mity/ville," which is how Lisa's friend says it. The movies are called the "Amityville" movies because the real story took place in Amityville, Long Island. Unless both girls live really far away from where she works, they would know how to pronounce it right. Then about 3 minutes later, Lisa says the street name wrong, even though that's one part of the address her friend said right three minutes earlier. She says "112 Oceans Avenue." It's Ocean Avenue. Unless they changed the name of the road, how would she not know this?
There are no mental institutions in Amityville, NY.
(at around 1h 13 mins) A spirit, or in this case a guy in a cloak tells a woman who summoned him "Kill them. Kill them all" while handing her a shotgun. Switching shots, all of a sudden, the man in the cloak shoots her after telling her to kill them all.