Lets validate some basics first:

1, 2) Have you stress-tested your CPU and ram?

3: the CRC is off only on two nibbles (between bits 4 and 11); and
nowhere else.  That usually doesn't happen with CRCs.
3) >> In the past I had some similar SATA controllers become corrupted
by some test-debugging code in an older version of the kernel.  Even
if the devices firmware is up to date TRY REFLASHING/'updating' THEM.
<<

4) Have you run S.M.A.R.T. self tests
5) If possible badblocks as well; once you've verified everything else.

Those are all possible and easy to test for causes of data-corruption.