Hi -
I'm having a similar problem. I purchased two new NUC i5s, with 3 sticks of Crucial 8GB RAM. I am planning on using one with 8GB of RAM, the other with 16. One of my NUCs will boot up just fine with any of the 3 sticks of RAM in the upper slot, but every time a stick is in the lower slot, solo or with an identical stick of RAM in the upper slot, I get a 3-blink LED sequence on boot, with no output to the display. Can't get it to behave differently regardless of configuration.
Is this NUC defective? Should I just send it back?
Thanks!
Andrew