...and I then set the AUX audio to HDMI ARC (video setting doesn't really matter since AUX will merely be playing audio from the TV's other sources)...
It matters that the Video setting be left blank (----) with the audio choice set to HDMI-ARC. Otherwise there could be a handshaking conflict with the audio return.
Main HT <> 976 <> 7200 <> Ultra-X12 <> sapphire ST2 mkII RF/LF <> sapphire SC center
sapphire ST2 mkII SBR/SBL <> sapphire SS SR/SL <> Verizon/DVR <> Vizio E70U-D3 <> Oppo UDP-203 <> Amazon 4k Fire TV