Sorry to hear that
In the almost-year I've owned the N5, I've been pretty happy with the build quality of the phone. The buttons still work and don't wobble, the case doesn't creak, and the soft-touch backing hasn't worn off. The screen's stayed scratch-free, too, and I'm still getting great battery life. The only issue I've got is that the USB port has become a bit temperamental for charging over the last month (it now seems to work reliably with only one particular cable -- I should probably get it replaced while I still can!)
I still think it's one of the best phones available -- right up there with the iPhone6, Sony Z3/Z3c and the Moto X; and for the price, the Z3c is really the only competition I can think of.