I had the exact same thing happen to me , at about 1500 rounds it started ejecting the magazine basically after every round fired causing stovepipes. Sent it back to Sig , it's apparently a known issue and they replaced basically everything inside the frame. I got it back made sure it ran well and promptly sold it. The perfect example of a gun you literally cannot shoot a whole lot to gain just a little bit more concealablity.You know I hesitate to post about my experience but it was similar to yours. It was a super reliable gun for quite a few hundred rounds and then all of a sudden it was like the gun was beating itself to death. I changed the magazine release several times because it was dropping mags. I started getting FTF and FTE and I was changing recoil springs often like I should. I think it's meant as a "shoot a little, carry a lot" gun. I really liked it but I sold it and moved on. Couldn't trust it.
Settled on the ECO as the absolute smallest 1911 I will carry / own.