I have posted here earlier concerning a Sig P320 X-Five which failed to remain open on last round. Sent it back to Sig.....little 4-5 week wait and they sent me a new Sig P320 X-Five which shot 100%, and they let me keep my original 4 magazines and sent me 4 new ones with the new gun!!!! (Thanks Sig). Liked it so much I purchased a second one (Ya, I know, Wife said the same thing) Well the new one, the second one i purchased had the same failed ti remain open problem. Same routine, sent it back, waited 4 weeks and it came back repaired....not a new gun. Talked to someone named John at Sig Customer Services, really great guy and he gave me the low-down on what was wrong. Had to buff the ramp, reform the slide a bit and buff that and another 3 items which I don't remember specifically but all involved buffing and reshaping. John said that the person doing the repairs was the best and would not let a gun out without making it perfect. John told me that they loaded up the 4 magazines, each with 5 different kinds if ammo from cheap to expensive and test fired the habdgun with 80 rounds of each...almost 500 rounds....tested with both strong and weak hand, and without a single FTF or FT lock back. A GOLD MEDAL for Sig Customer Services in my mind and a Kudos to the man who did the repairs. I can't ask for anymore other than to test fire the gun before they have it leave the factory.
That certainly sounds like you had good CS both times. However, it raises the question on how SIG’s flagship pistol could make it out the door so poorly made/finished? That, IMO, does NOT speak well of SIG’s manufacturing process. Several years ago, they had a CNC programing error and a large lot of 556 Classics went out before they caught the error. I had one and like you, SIG ended up sending me a new 556 which I appreciated. However, then like now, the 556 was their flagship rifle/pistol and their attention to detail still appears to be lacking. That is disconcerting.