I wouldn't rule that out. All of the hardware was reused on the rods they came from, to keep balance. I didn't think that it would make a difference, but I'm wondering if the high ring lands and high compression/ heat said otherwise.
The way it started making a sound immediately got me thinking rod bolt/ nut issue.
I'll know a lot more when I take it apart, but yeah, it could easily still be a hardware issue. I'm going loc-tite next time with new nuts, even if it's not the issue.