So, my SP5k (tricked out to MP5k configuration by TSC) experienced it's first failure with about 2,000 rounds through the gun. It was a stovepipe FT -eject jammed between the ejection port and the next round. It was while using an MKE mag. I ran another 120 rounds afterwards without issue, using HK German mags. However, I want to keep this gun 100% reliable (part of my HD plan). Should I replace the extractor spring now as a preventive maintenance measure?

Sure, it can’t hurt.

Buy a few of the springs since they are so cheap. Only takes a few seconds to switch out.

Sounds like it is possibly a mag issue but for some reason people like to throw money at these things.