Continuity mistake: After Esther suffocates Daniel in the hospital, Kate slaps Esther in the face. The hospital staff then hold down Kate and she drops her iPhone, screen down. The iPhone starts ringing, even though the screen is facing the floor. In the next scene, it is still ringing, but with the screen facing upwards.
Continuity mistake: Early in the film, at one point, the family returns home and it is snowing lightly. The windshield wipers stop and there is a brief overhead shot of the mother near the car and too much snow has collected on the windshield of the car. Not enough time has passed to allow that much snow to collect on the car.
Continuity mistake: When Esther is in her room and you are seeing that she is not a little girl but in fact an adult, she takes her teeth out. They're the nice teeth covering her bad ones. However when she sets them down, you can see that they are the wrong teeth. She has taken her bad prop teeth out and set them down, when it should have been the nice ones. You can see right before she takes them out that her teeth look nice. When she sets them down they are the bad set.
Other mistake: When Esther comes into the living room to attempt to seduce John, he is drunk and the first few shots of her are blurred as though it was from his point of view. The problem is that the camera is a couple of feet from the couch. From where John is sitting, the point of view shown in the blurry shots is impossible.