Sorry don't know why it posted early with just the first paragraph. Gun is completely stock and new. It now has around 400rds through it. It seems a little better but I still get a failure to extract or eject every 30 rounds or so. I've been running mostly the sig load, FMJ 180g @ 1250fps.
I have a 29SF and I went straight to a Wolff guide rod and calibration spring pack. I got it mainly for when we go hiking and planned to carry Buffalo Bore 220gr Hard Cast when we do. I decided to start with the 21lb spring and would adjust from there if I had any issues. I didn't, the 21lb spring successfully cycled the Buffalo Bore, my SD round which is Speer Gold Dot 200gr GDHP, and my range ammo which is 180gr Freedom Munitions or 180gr Remington UMC. All shot out of the stock barrel. The BB will be the hottest thing I shoot and with the cost it won't be too often. Just enough to keep me on my toes with it if I ever needed to use it when hiking.
However with you have a 20 and the single spring RSA, your results and needs may be different than mine with 29 and dual spring rsa. Look for user WeeWilly, he was very helpful to me when I had plenty of 10mm questions and has a 20 with plenty of user experience with it.
Also, first thing I would ask and check is your extractor spring and striker block and if you ever had the slide plate off and extractor plunger out make sure you put the spring back on right, next make sure your striker block moves freely. You could have some grit or a burr in there that may intermittently be affecting the extractor to move freely. Wouldn't hurt to take them out, inspect, and clean up. Here is link to a quick video showing removal. I don't know this person just first video that came up shows removal. Good luck!