After 2 days of mining I turned both R4 off to just to put power usage meter in line.
When powered back one hash board died... need to send whole R4 unit back for repair

Well that sucks. And you are the first to report a dead batch 2 r4.
So some questions to ask:
1) what was the psu you used?
2) how was the room it was in? by that was it really hot or really cold? above 90 f or below 35 f ?