Here's a new one:

Last night my Arc-based home theater set up experienced a disconnect of the volume control  hand-off between LG display to Arc via HDMI. Could control volume via Alexa voice or sonos app, but not with the LG or any other remote control.

Unplugged and rebooted everything this morning and the correct hand-off happens correctly again. Even faster than before. I thought this could be an artifact of cloud-based operation, but that might be a stretch.

I was dreading contact sonos customer service....