How long have you owned this particular PSU? What model is it?
I had to replace a PSU recently. (Generic brand, 650W, “Bronze 80+” rating.) I went with a Corsair instead.
Luckily, I did not lose any data nor cause any pool corruption. The only drives affected were brand new, and responded by constantly spinning down and parking the heads.
EDIT: Reading this thread again, the parallel 2.2 million checksum errors on (two different disks) makes it look like a cabling issue as well.