Check the board for loose or missing screws. Also look for shorts. A big issue with the cubes was excessive Flux and sometimes solder flakes getting stuck to the board and shorting out compenents. I haven't seen this with the prisma/tube's yet, but worth giving a lookover.
Wow I should know better. Every screw was loose (literally all of of them). Been hashing now for 2 hours no spikes in HWe's and no board resets.
Wish I would have thought of that yesterday. Will keep you updated.
Damn...
EDIT: Well that was a premature celebration HWe just spiked and boards started resetting. The common denominator here is the controller there is no way this many boards are defective.