The Dark Knight DVD scene freeze?

its not a big issue, but after the scene where Harvey is locked into the police truck, and he gives rachel the coin, when the door to the police truck closes, the scene pauses, for like half a second on my dvd. i know this because the cop in the background suddenly freezes and so does everything, but after thay everything runs normal. so, for some reason, that scene freezes, but you dont really notice it unless you pay attention. are all the other dvds like that or is it some kind of small defect? again, not a big deal, but im curious to find out.