When the family truck is shown from the outside, it is clearly marked as a Honda Passport. When Wayne is seen inside driving to see the mayor, the steering wheel sports the Dodge "Ram Head" logo in the center.
When the daughter is in the bathroom and grabs a glass (which already has water in it), there are three items on that same cabinet. Also the sink has a brown tube to the left of the faucet and the bar of soap is to the right of it. In the same bathroom minutes later when the woman from the historical society comes over, there are only two items on the cabinet and they are rearranged. The sink now has no brown tube and the bar of soap is shown to the left of the faucet.
Some scenes take place during daylight. Then logically continue in the house, seconds later. But the windows appear dark, no daylight.
(at around 15 mins) the wife goes into the bathroom and opens the door towards her (into the hallway) yet when she is in the bathroom with her husband, the door is opened into the bathroom.
Mrs. Winston entering the Downs's house searching for them and forced by a demon power she's boiling her head to death! Note: The stove is boiling the water in just 2 seconds!!.
While the Sheriff is taking out the trash bag and later talking to his wife, it appears that his pistol is unloaded, in that there is no magazine in the pistol grip. Something an experienced officer would not do.
When the Sheriff goes upstairs with the gas can and enters the room where is wife has been hung, her eyelids flutter.
Salem does not have, and has never had, a Sheriff. Sheriffs are county law enforcement officials, and the only local sheriff is the Essex County Sheriff, who has no actual law enforcement power. The correct position would be the Salem Chief of Police. Additionally, the uniform patches are all wrong.
At 35 minutes, the sheriff enters his house and takes off his boots, revealing bare feet. Yet the sound of him walking throughout the house afterwards seems to be the sound of boots or shoes on the floor.
When Wayne removes a packing box from atop the car, it is obviously empty from the way he handles it.
When talking to Mike the deputy after the grounds keeper hangs himself, you can see someone's hand in the trees.
The movie is set in Salem, but the foliage is clearly Californian - including a large Kumquat tree - which last I checked do NOT grow in Massachusetts.
(at around 19 minutes) after Mike leaves the Sheriff and his wife to talk on the porch, reflected in the transom overhead on the left side of the screen, the top of the boom mic's blimp appears briefly.