Gaffes

The window changes position between shots slightly when Tim talks to Lily in her car.

At 01h16, when Amanda drinks the glass of fruit, we can clearly hear she put it back on the table before falling asleep, on the next shot, when Lily leaves, the glass has vanished.

At 01h11 30, when Mark's playing tennis alone, on the first shot, facing him, we can clearly see the playground with almost no tennis balls, when the camera comes his side, the playground is full of tennis balls.

When Amanda is teaching Lily the technique while watching the film, Lily's hair is either above her right ear when she is filmed from the front and laid back behind her right ear, when she is filmed from the side.

Amanda states that her therapist diagnosed her with anti-social personality disorder (among others). No one trained in psychology would ever diagnose a teenager with this disorder because all teenagers, technically, fit on the spectrum. Also, neither girl is a true psychopath as both show hints of remorse at times.

When Lily shows up to valet her car, it clearly sounds like a gas internal combustion engine but once she exits, it's a Tesla (Electric and therefore no exhaust noises).

The outdoor chess set initial position had the queen and king swapped. White King should be on E1, it was on D1.

Mark's bicycle wounds disappear very quickly.

Near the end of the film Lily arrives for a lunch meeting in a white Tesla Model S that includes added sound from a gasoline powered car shutting off with a distinct putt-putt-putt. The only sound that should have been heard other than the tires on the road is the parking brake clamping the back wheels.

When Tim shows up at Lily's house with a handgun,he ,Lily and Amanda argue about murdering Lily's father.A brief full shot of Lily shows that she is barefoot.Later on,when Amanda and Tim are on the floor wrestling and Lily puts the gun to his head,a brief shot of Lily's feet shows her wearing slip-on flats.

(at around 00:35:00) When Lily opens her eye the cameraman and camera are clearly visible in her pupil's reflection.

When Lily surfaces from holding her breath underwater you can see someone in shorts standing in the background to the right.