The bottom of my new 21.5" iMac has some play in it (very little)... the black part and the aluminum aren't completely flush, but only over the middle 6 inches or so, right above the apple. Should I be concerned about it? I don't have any other problems with it, so I am hesitant to try to switch it out and end up with some of the other issues people are having. Any input would be great! Thanks!