When Derrick hands Cathy a half-filled glass after Cathy confronts him about raping Naomi, she throws it to the ground but there is no liquid inside when it hits the floor
Towards the end of the movie, the scratches on Derrick's face appear to be almost healed. However, in the final scene the scratches are shown to be open and fresh for one shot, then are healed again.
When Jones comes rushing in to tell Derrick that Travis has a gun, she is completely dry, yet she was just out in the rain.
When Derrick goes to the rooftop during a house search, his hair is already wet, although he hasn't been exposed to rain yet.
Towards the end, when Cathy and Derrick are angrily discussing in their loft apartment the uncertainties of the plot unfolding, Derrick pours her a drink (Laguvulin whisky) from a bottle which he sets beside him onto the shelf of the bar on his left: when Cathy next shot storms out, the camera angle from her P.O.V. leaving, shows Derrick still leaning against the bar - but no bottle anymore.
During the fight between Beau and Derrick, Beau punches Derrick in the face, but James Marsden's head moves in reaction to the punch before it has even landed.
When Beau and Derrick are fighting outside of Naomi's apartment building, they collide with a door beside some greenhouses and plant supplies, and the door cracks against their weight. During the commentary, the actors and director themselves reveal this was a mistake.