So we are referring to the internals of the gun. For the externals, do whatever your heart desires, that is one reason for so many pages.
Most of the issues are caused by mixing and matching parts. QC is something TM has down pat, and when you mix that with drivetrain components that are not to the correct spec, you have issues. I have never run ProWIn Mags, but if you are having issues with them running with your aftermarket bolt carrier, I have a hard time agreeing that it is superior.
My stock bolt carrier and mags run like a champ and have for thousands of rounds. The only issues I ever ran into involved running an aftermarket light weight bolt...which was remedied by going back to the original. From near 0 degrees C to over 30 degress C, this thing has run. Sure, slower at colder temps but better than any gasser should and anything above...It just runs.