I fixed the issue on my rig, so I am sharing what worked for others who may have the same issue. Turns out it was a riser issue after all - but one that I caused (and not a hardware error).
Two of the small riser adapter cards were incorrectly paired via USB with the wrong riser.
My riser cards, which are “VER010-X,” come with riser adapters that state, “VER008S.” See screenshots, below. When assembling the rig, I saw the mismatched version labels and opted to replace the small riser adapter cards with others I had of VER10. Big mistake.
After pairing the little riser adapters to the correct risers they came packaged with, the rig mined for 12 hours without throwing any errors. Also, the wattages and temps display properly on all cards. Feeling bold, I added a couple cards and another PSU to be safe. See screenshot below. System has been stable for approx. 12 hrs. Hope this helps someone. Cheers.