I have a similar problem.
Intel NUC D54250. Latest Bios. If plugged in via HDMI to my sony bravia TV, I get video+audio no problem. If plugged in via HDMI to my Pioneer SC-79 receiver, I get video only, NO audio. I have tried everything. I am 100% sure the receiver is working fine (it works flawlessly with apple tv into the same HDMI socket).
What the ?? Please intel send us an update on this.
Peter