Marc MERLIN posted on Tue, 23 Feb 2016 16:19:44 -0800 as excerpted:

Cabling is indeed a likely culprit, I'm just surprised that if it's the
case, the sata layer is showing me nothing (I'm doing tail -f
/var/log/kern.log and usually I'd see sata or PMP errors there)

That /is/ surprising.  No explanation, there, tho I don't know enough 
about such errors to know if they /always/ tend to show up in the logs, 
or not, only that mine generally have.

-- 
Duncan - List replies preferred.   No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master."  Richard Stallman