I've had a fist Gen 20 since they came out, fired factory, reloads, lead, copper, blazer just about everything and the few feeding issues were with Sacco 200grn lead. My favorite load was with 452 AA (sadly all gone now) but have used #5, #2, WSL, WST, N320 and now 231. You may have to make this into a science project, go with what you know works and replace one thing at a time and log the results. Have you analyzed each miss feed to see if they are in the same position ETC. Talk about a gremlin...