Nic, you wrote: "I was able to play Dolby 5.1 and Stereo without issue, using both the AV/R and not using the AV/R."
Dolby Digital 5.1 is not the problem, Dolby Digital Plus is the problem. Are you sure you're bitstreaming to the receiver? The way to test is with House of Cards, which is DD+ and unplayable on my NUC, except in stereo.
This is not a hardware issue with my receiver, which plays DD+ just fine with my PS3 and my laptop (Nvidia 770M). My NUC is 100% up-to-date on everything. Now, I honestly can't verify the HDMI cable, since Intel chose to use a mini-HDMI connector, but a cable issue is really unlikely considering how many people have reported the same problem on this thread.
Let's just say this needs fixing before House of Cards season 2 begins. The whole reason I bought the NUC was to dump the PS3.