Hey Flying Dach,
What part of the body is PVC? If the entire body is PVC, you might be able to remedy the warpage with a hair dryer. It is no excuse for Daiki Kogyo to ship it in such a condition, but to me it's even worse if the silly thing was designed with a mostly PVC body, like a garage kit. The steyr parts and really most of the gun should have been ABS.
Just cheapness, no excuse.