Good luck. I used to be a huge Sig fan. Back when they were a German gun maker that sucked at marketing and sales. Now they are an American marketing company that sells guns. And since Cohen took over SigUSA, stupid shit like this has been the norm. I know he saved Sig from financial ruin, but some of those choices have taken a former top tier brand and made it a joke. Having guns released that have to go through several Gens to get right, QC issues like the OP has on what is supposed to be a premium product, to selling rebranded cheap Chinese accessories to go with your 'high end' gun.
But if you call Sig, let us know how they explain how their ammo doesn't fit in their gun. Total systems provider and all.