I have not moved cables between controllers.
md126 is connected to my gigabyte mainboard sata controller
md127 is connected to 2:00.0 SATA controller: ASMedia Technology Inc. Device 0625 (rev 01) (prog-if 01 [AHCI 1.0])
which is a pcie plugin controller.
but i have replaced cables with brand new ones, and the ata device errors remain on the disks that have new cables.
I guess your suggestion would be best, move the md127 array to the onboard controller and test.