In the opening decapitation, blood spatters across the car before the decapitation.
The girls escape their room early in the day, but when Ike and Addley are interrupted to go rescue their mother from Queenie, it's almost night, as evident by the low light. Then, it shows the girls escaping into the woods and it's earlier in the day again, as there's much more light.
At the beginning, when the couple are attacked in Mother's car, there is blood on the woman's clothes before the guy is attacked.
When the girls are kidnapped and put in the sleeping bags, they are wearing night clothes as they were in bed. When the sleeping bags are re-opened in the house, however, they are now fully clothed (with one even wearing jewellery) with no explanation of how this happened.
Trina's gag changes positions as she watches through the window. Additionally, the stuffing in her mouth disappears altogether.
Abbey chokes one brother to death, but the thing she is coking him with doesn't cover his nose. He could breathe through the nose and survive.
In the beginning of the film when the couple are in mother's car the man is obviously a dummy.
The TV that Abbey drops on Ike's head is obviously empty, with no working parts in it.
Mother is still breathing after being choked to death.
Abbey's cuts on hands are too big, clearly revealing fake skin used for the wounds.
When one of the brothers starts hitting the girl on the car at the start of the movie, it's obvious he is missing her.
It is seen that Jackie lives in New York City at the beginning of the film. However, her car has New Jersey license plates, if she really were a New York resident of course, her vehicle would have New York license plates.
The city scene opens with a caption that reads "Chicago" yet the doorman states that they are in New York.
Trina's address on the telegram is 210 Alameda Road, Beverly Hills, CA 94510. Alameda is one of the main streets in downtown LA, but there is no Alameda, Road or otherwise in Beverly Hills, and zip 94510 is in Solano county, north of San Francisco.
The blonde girl is lowered out of the window in a sleeping bag by her friend, yet comes back upstairs straight after to free her friend, and does not even have to unlock the door. If the door was unlocked, she could have just walked out rather than going out of the window.
(at around 36 mins) When the old man is talking to the girl whose mammoth left breast takes up the right side of the screen, the boom mic dips into the top of the frame.