***** happens. But, there often is a reason for it. Find the rotor that is warped with a dial indicator and be sure the calipers and flex hoses are functioning properly. Check to be sure the wheel flange is clean beneath the rotor.
I can tell you from thousands of rotor installs, that every once in a while one does this. Send it back, I'm sure they will stand up for it.
Bosch Master, ASE Master, L1
33 years MB technician