The opening Scripture quotation is listed as "Peter 5:8." There is no such book in the Bible; it should be "1st Peter 5:8".
In the aftermath of the car crash, it's revealed that the young boy was propelled through the windscreen from the inside of the car. However, it is evident that the hole punched into the glass was made from the outside of the vehicle. A projectile puncturing through the windscreen from the inside would leave the glass shredding and fragments on the outside of the car.
In the end, the Mechanic confesses on the walkie while the entire time trapped inside none of them thought of using it or even trying to see if it worked.
Initially Detective Bowden's beard is obvious and thick. Shortly afterwards, his beard is clearly not as thick as if he has shaved.
9 minutes into the film, as the elevator door closes, the last Passenger puts his arm in the way to stop it, but it is not visible in the mirror. This reveals that, to avoid revealing the camera in the mirror, they superimposed video into the scene.
The Mechanic opens the roof hatch on the elevator to help calm down the Guard since he is claustrophobic. However these hatches are always locked from the outside, the point of the hatch is not to allow passengers to get out in an emergency but to allow rescue personnel into the elevator. The last thing emergency personnel want in this situation is panicked passengers climbing around on top of the elevator or even worse trying to climb around inside the elevator shaft.