Cracks at the corners

The shell itself fits initially properly, visually gives a good impression and fits comfortably in your hand.
However, formed on the second day hairline cracks at the corners.
While the shell still sat firmly on the iPad (3), but not visually I thought that was so good and got the shell first returned.
Maybe it was a Monday model, let's see how does the compensation cover.

Addendum 06:03:13: Good for nothing, now get the second covering and after a few days the same: Cracks at the corners. The whole without fault of their own. Cover attached, also fits well and after two days form at the corners crazing. Not be excessively stressed our iPad 3 also. Located in the living room, no sunlight, no wild kids and no tense game attitude and still cracking. Too bad. So I have the envelope send back this time but then without replacement. Unfortunately.