Thanks for the extra info, certainly points to the board having an issue.

Due to having other equipment and a lack of space and time, I'm considering selling now.

If anyone is interested in purchasing my Cointerra, hashing on 1 board very happily and I guess potentially fixable, please drop me a PM.  I'm open to offers.  Maybe if you have the same issue you can make 1 good machine and have a lot of spares, or have a much cooler 1/2 power box...