I bought a used Para Ordnance GI Expert a few months ago. It's having a feeding issue. Couldn't get through a magazine without having a round fail to feed. The round will partially feed, but stop about a quarter inch from fully seating in the chamber. I was using the factory Para mags.

I cleaned the gun, including the extractor, which was filthy. It helped a little but not much.

I bought a Colt mag and took the gun to the range. Got through about 75 rounds without an issue. Then it happened again for three straight mags.

I can push on the slide, and the round will fully seat.