On a Sig? Good heavens no!
Solution: Give me the P220, and go get a P226 MK25, 20-round mags, and +P 135gr Hornady Critical Duty. :D
P.S. Are you still complaining after Sig fixed it? ....or is it still problemmatic.
P.P.S. There are issues with certain extended mags having too much/too little spring tension and this may be one of the symptoms....
P.P.P.S. Tried different ammo yet?
P.P.P.P.S. Remove one mag spring, stretch it by 1-2 inches. and reinstall it to see if the situation gets better or worse.