Returned one NUC to NewEgg. New unit received in about 10 days. Very simple return did the transaction on line over internet about in 10 minutes on Sunday..
Returned one to my retailer. He had Intel send me a new unit, after which I returned the defective one.
All in all, the process was painless.
I fear I have to start over again, the second unit died on me yesterday.
Will call my retail shop tomorrow and ask what can be done.