Crew or equipment visible: In a fight scene near the climax, a member of crew (complete with camera).
Factual errors: During the police line up, each of the men are told to turn around and face J.C. directly. Police line ups are never done in this manner. They are done with mirrored glass to protect the identity of the victim or witness.
Audio/visual unsynchronized: When Horowitz is going to solitary, his lips do not match what he's saying.
Boom mic visible: When O'Brien and Horowitz are talking in the shower, the shadow of the boom mic moves back and forth on the wall when O'Brien walks away.
Revealing mistakes: Position of Paco when leaning up against the locker.
Revealing mistakes: Obvious mannequin that Mick hits into when crashing the car.
Continuity: In the scene where Paco's mother is packing her dead son's belongings away, Paco says to his mother "I have to do it!" It comes up as the same words on the screen twice. But when he says it the second time, he says something different in the language he is speaking.
Continuity: In the final fight scene between Mick & Paco, Paco has Mick against the bunk, Mick is standing on the left of screen, while Paco is standing right of screen, and stabs him in his right shoulder. Then the camera cuts suddenly to both Mick and Paco in another fighting position, with Mick now on the right side, and Paco on the left, as if there was a cut in the film.