It is most likely that the ring (stopper) on the cartridge came off during transportation, or that you have forgotten to take off the O-ring1 when replacing the cartridge. It is highly unlikely that the leaking has been caused by a mechanical fault in the appliance.
1O-ring
Small, round rubber gasket that prevents leakage when connecting the various pipes to the appliance.
Small, round rubber gasket that prevents leakage when connecting the various pipes to the appliance.
