Sorry to revive an old topic, but I was wondering if your drives were failing in the 5th slot from the top. It looks like I have the same case as you, and I’ve had a drive fail in that same location twice now. Both are Seagate Ironwolf NAS 12TB HDDs. Bad block on the first, and bad block on the 2nd drive. I just got the replacement drive and it died after a few days. Really weird. System is on a UPS with 750W Gold PSU.