Originally Posted by JARblue

Firmware was definitely my first thought. I was really starting to wonder about the ARC thing, too, since I found no indication in my research that there could be incompatibilities.

After speaking with both Sony and Samsung, I went back to Best Buy and had a chat with their staff. I decided to start with the easiest option, and just bought a second 4K HDMI cable to test it. Voila! Since I had to fit the new 4K cable through 3/4" smurf tubing I have already installed in the wall, I had to trim the head around the connector on one end. It looks like I must have compromised it during the trimming process. I will need to purchase and fish another longer cable through the wall later. Could have been easier, but definitely better than having to return either product.