When the heartless woman is escorting David out of their room, she clearly has blood splatters on the backside of her calf. As she chases David through the halls, the blood on the back of her calf disappears. When David shoots her with the tranquilizer in the back, the blood has reappeared on her calf.
After the heartless woman falls down from getting shot by David with a tranquilizer gun, her skirt falls open high enough to see her underwear. When David approaches her, her skirt is now covering up the underwear.
In the shopping mall, whilst the female officer is questioning the kneeling woman who says that her husband is away, the officer goes and crouches down to look at the kneeling woman's shoes and puts her hands on the soles of them. In the next shot suddenly both of the officer's wrists are resting on her thighs near her knees, with her hands nowhere near the kneeling woman's shoes.
When the nosebleed woman is reading her letter to her friend who did not find a partner, she begins to react to the friend slapping her just before it happens.
During the opening scene, the camera operator can be seen adjusting the lens in the reflection of the drivers door window.
When David was trying to see if the other person was wearing contacts while in the woods, whenever he gave a direction to point his eye (left, right, up....etc), the other character would move his eye in the correct direction slightly before David would say which direction to look.