Have you shot any heavy field loads thru it?
Sometimes, not all, a semi-auto needs a couple of boxes of heavy loads, the largest the chamber will handle, IE: 3" if it is a 3" gun and so on, to wear everything in and mate the pieces. They may look finished when they are torn down and cleaned, but may have some slight burrs that the heavy loads help remove.
I bought a shotgun locally that the original owner claimed was defective, store wouldn't give him his money back, manufacture took it in and "repaired" it, and still he could not get it to run. I bought it for less than half of what he paid, ran 2 boxes of the cheapest 3" duck loads I could find thru it. First 10rds, 3 FTE, second 10rds, 1 FTE, remainder of the 2 boxes, not one FTE. The gun has never had another 3" load in it and routinely shoots 7/8oz loads all day with out a hiccup. Point is, don't rush to give up on it, one of the best guns I have, made me see cross-eyed for a couple of months until it finally broke in.
NRA Life Member