Finally after much gnashing of teeth the raid6 array was recovered.It had lost a disk, and its host computer (a ASUS mobo system @2009) started having issues.

We setup a nuc11 for it, and memory and a SSD for its OS. The array was put into 4 unit containers. The reassembly, that was lasting days on the old iron only took < 1 day. It is now clean. No more dirty and degraded.

I got bacula (community) up and running and am taking a full backup to an external disk.