Default Z1s and Sony/Tmobile Return Policy

So, I've had my Xperia Z1s for a few months now, and I've been using the Elite Body Globe case that tmobile sells. For some reason, these hairline fractures keep popping up without me even dropping it. One on the front and one on the back. They aren't connected to the ends of the phone either, which makes it so strange. Anybody know what it could be and if I could get it fixed?

Sent from my C6916 using XDA Premium 4 mobile app
too lazy