I know it's been a while but I sent my P229 back to Sig and the work order said the following:
The slide catch lever has been modified by source outside of Sig Sauer.
Replaced the slide catch lever.
Polished the locking insert, the feed ramp, and the chamber.
Replaced the damaged extractor.
I've owned this pistol since new, I removed the plastic it was wrapped in from Sig. No one but Sig has touched this gun. It was sent back to them once before for the same jamming issue and they said there was nothing wrong with it, I doubt they inspected it and didn't have a jam while test firing it.
On a positive note, I fired 50 rounds of 185 grain and 20 rounds of 165 grain and it worked flawlessly for the first time.