Thank you for the input
but I think I may have fixed the issue or found some larger issue in my build I am not 100% sure yet...
I am still working from home from the COVID WFH orders and had an extremely slow Monday today. I pulled my rig into my living room and started tearing into it to poke things with my multi-meter and do some basic testing of the PSU. Unplugged the three SATA power plugs I have (2 Corsair RGB control modules and one for the H150i) and unplugged the 2 8-pin PCIe plugs from the GPU and powered the machine on. It hit BIOS and threw the expected GPU error so I pressed the power button to shut it back off putting the system into an S5 state. No fans spinning and no RGB on as expected as the GPU 12V and the H150i SATA plug are disconnected. Checked the same PCIe power plug and other than a small bit of residual voltage that drained quickly from the on plug capacitor, my multi-meter showed 0V.
One at a time I plug in each SATA device and repeated the test and each time after power down I read 0V on the 12V rail. I even went as far to test the pins on the GPU itself to see if it was back feeding somehow, still 0V. I connected the GPU power and booted into Windows and did a shutdown from there. Still 0V.
At this point I don't think it is the PSU that is the issue. I was running it on the same UPS with the same power cord but it was in my living room VS my office. The ONLY other difference is I did not have my VR setup connected.
Moved everything back into my office and plug everything back in. Boot into Windows then shut back down and everything behaves normally with 0V on the 12V rail.
My only guess was one of the SATA plugs wasn't connected correctly and me unplugging and plugging them in corrected it? I am going to keep an eye on it and just call it my PC throwing a temper tantrum for now.