Thanks Towen. If it does come to that, I guess I should hook up a spare HDMI cable, one that isn't connected to anything, to see if I still have the audio dropout. It could be just having something plugged in there could cause the issue, but at least I know there is an option if all else fails.Yes.
I have used ViewHD 3x1 switches ($40 at Amazon) and 4x2 matrix switches ($60 at Amazon) for several installations for work. They handle UHD and lossless audio and have SPDIF outputs too.
And if all else fails, I have basically a walkway behind the tv, so when I want to watch a movie, it's pretty easy to just walk back there and unplug the HDMI cable. Hooking it back up is slightly tougher as the Vizio has odd inputs in that they are tucked up in there and plugging them in is difficult at times.