Cheap copper is very real possibility for leaking gaskets, everything else made now a days has gone to a cheaper version! Why spend good money on new copper when so much recycled is out there.
Machining finish could also account for a leak. To rough of a finish can leave small grooves to deep for the gasket to get in to leaving multiple paths to leak out of. To smooth of a finish can let the head move around since there is nothing to bite into the copper with. As the head moves with heating and combustion pressures, the seal never sets in one place.
Time to pull it apart for a complete diagnosing, and follow up to the problem.
Joe
