I saw your pic, and agree that it was unnacceptable, no disagreement there.
If the dude's jaw part is indeed missing, then it should be replaced (of course). I just find it questionable that it wasn't just a mistake on his end, considering the foot he called "broken", and the claim of so many other items being "broken".
I actually broke SEVERAL parts on my endo because I wanted further articulation in the head/neck, but I'd never label my own mistake as a QC error, as I'm sure many people do after "ham hands-ing" a delicate piece.
Actually, a did have one legit QC issue on mine, but I got a replacement part, and was even able to glue the original part, so if it re-breaks I will use the extra part. If curious, it was a connection hinge for one of the big thigh pistons, where it connects to the pelvis on the rear bottom side.
I didn't have to send back a whole figure or anything, so I'm very satisfied. The other parts that broke were the neck rods where they connect to the base of the skull. I pushed the head too far...but I actually like it better because now I can get much more expression out of his poses, and the rods can be placed individually where ever I'd like, so you can't even tell they're broken/disconnected.