When Stowe enters the police station after recovering from his coma, he is wearing a necklace. In the next shot, during the same conversation, it has gone.
When Det. Anthony Stowe wakes up form his coma, he opens his eyes wide and they remain open as frozen. In a follow up shot, they are less open. And when his gurney reaches his house, his eyes are closed again. The opening of the eyes was the cause for him be to put in his wife's care at home, instead of staying at the hospital's trauma unit.
In the opening, when Callaghan asks for the lock combination, the woman says the code is "666". When the camera pans down the lock has 4 sliders, not 3.
The doctors say they took the bullet out of his head, as it was lodged in his skull. However when he is shot there is clearly an exit wound as blood bursts out of his head, implying that the bullet exited.
At the end when Callaghan is holding Stowe's wife hostage in front of the helicopter, Callaghan fires at Stowe once. When the camera comes back to him holding Stowe's wife hostage, we can see and hear her shriek as another gunshot is seen going off but not heard (the puff of smoke is clearly visible).
When Stowe is talking to Chad, towards the end, the camera is on Chad over Stowe's shoulder. When Stowe is "talking" his mouth clearly is not moving and Chad is nodding his head.
During the hostage scene at the end of the movie in the warehouse, as Anthony Stowe is driving his car towards Callaghan's men, the film crew is clearly visible on the right hand side through the windscreen.