After moving and setting things back up we seem to be having a bit of an issue.
We have a sound bar that supports ARC; it's a Signa S2 to be exact.
The 65S4 also supports ARC (HDMI3).
The TV remote does change the volume on the sound bar; and the sound bar changes its volume/the TV's volume, nothing wrong there.
The issue right now is that no sound is coming through the sound bar.
Setting the input on the sound bar to TV (Via HDMI) results in no sound.
We've had to plug in the optical cord and change the input to optical just to get sound. It's not the end of the world, but it would be nice to get ARC fully working; so we don't have to use HDMI + Optical.