The factory parts thing is going to be SOP for any gun company. No manufacturer is going to warranty a gun with aftermarket parts.
Interesting you're having stovepipes with your mk iv. I just bought one this past week and had the exact same issue. The extracted rounds were hitting the edge of the rear feed lips on the mag before they got to the ejector, and that was causing the stovepipes. It was happening 3-4x per magazine. I rounded off and polished the front of the rear feed lips on the mags and it's running great now...200+ rounds today with zero issues. If for some reason it comes back from Ruger still not working, that's likely the place to look to fix your problem.