How long have you owned this particular PSU? What model is it?
Its this one: CoolerMaster ELITE NEX White W500
I got it back in August when I upgraded the hardware. Before then it was running flawlessly in an old Mac Pro tower (until it wasn’t).
Reading this thread again, the parallel 2.2 million checksum errors on (two different disks) makes it look like a cabling issue as well.
I agree, and it may have been. I had re-seated all connections a couple times in troubleshooting, but maybe by then the damage was done? I suppose the best case scenario is that it was bad cable connections and there’s nothing to fear going forward (having made darn sure they’re secure now). Ideally I’d like to find a way to confirm some scenario with a reasonable amount of certainty though, so that’s what I’m trying to do now.