Exchange them at where you bought them!!!, like I did with the DVDs I got from TAU

Next time when you get some DVDs, "Shake" it and check the outside packaging before you open it. 如果是固定DVD的小卡榫斷了, 搖一搖可以聽到喀啦喀啦的聲音, 而且如果DVD片子已經沒有被固定住了 , DVD片子會在裡面滑動, 可以聽到很大聲的喀喀的聲音. If you hear something strange or if the case is damaged, don't open it. Get another copy at your local Bestbuy, Walmart...etc, keep the good one and return the damaged one to the local store. If you opened your DVD like I did, you can only exchange it thru where you got them. This could take some time.

Good luck