When Mattie is pouring Carol a glass of wine, and she hands it to her, she was already holding a full glass of wine in the previous scene.
When The Stepfather is arranging a victim's house and body to look like a suicide, the victim's dead body, hanging from a noose, blinks.
Early in the film, it is established that Jerry/Gene got the idea to move to the Palm Meadow Estates after seeing it mentioned as the locale for a grand prize on "Dream House". However, the game show only aired from April 1983 to July 1984, and had been off the air for several years when filming took place, in 1988. Additionally, after host Bob Eubanks asks announcer Johnny Gilbert to describe one of the homes offered, the voice-over heard on the new cut-in footage of Palm Meadow Estates is not Gilbert.