Shin,
He stated earlier that 3 shooters tried this gun and all three got the same results. He tried it with and without a slipon pad for his long LOP. He tried different choke tubes.

I think he's down to: "...there is something terribly wrong..."

CSM would no doubt pattern the gun themselves when returned and give their assessment. They may elect to replace the barrels or even the whole gun if they agree.