It's the only diagnostic that seems to make sense right now. Everything works perfectly if it's not using one of those SATAIII ports. Luckily this board has two more ports using a different controller (Marvell), so I'm using those now for the two main SSD's, and the other one plus the boot disk are on the SATAII controller. There is also an external USB drive used for backups.

I just switched the stats back on as they've been running just fine for the last 5 hours or so. No errors at all.

Going to buy up some spare parts with the donations I received and slowly build up a complete hot spare.