Factual error: When they show Alex's partner in the hospital his heart rate is showing 35 on the monitor. His heart rate is not that low from the EKG pattern.
Factual error: When during The Novak Element show Novak tells Sellars that Omnicorp's stock went through the roof there is a very simple math mistake. The stock goes from 520.70 to 1129.52, which is an increase of 608.82, or a 116.9% increase (608.82/520.70). Instead, in the movie they show the increase to be 53.9%, which is wrong, because the starting base is not 1129.52 (53.9% is 608.82/1129.52). (01:11:05)
Audio problem: When Dr. Norton disassembles RoboCop to demonstrate to him the reality of his situation, the movement of his lungs do not match Murphy's speech. (00:33:30)
Continuity mistake: During the gunfight in the arms dealer's hideout, Robocop enters brandishing his futuristic 'M2 Battle Rifle' which then immediately changes to an MP7 in the next shot. This error gets particularly blatant during the following shots from his POV, where he's shown still firing the M2 in his HUD, only for the scene to immediately cut to show him firing the MP7.
Continuity mistake: When Murphy's car blows up on the drive way nothing else is damaged. No damage to the house, broken windows or burn marks etc., and no damage to the house next door.
Chosen answer: He most likely has an artificial heart or some type of system that circulates his blood, this system doesn't necessarily have to take the shape of a typical human heart. However if his biological heart is still functional, it may be behind the lungs.