Hello @Dave330, welcome to the Sonos Community!
I am sorry to hear you are experiencing issues with volume changing automatically on the Sonos Arc Ultra.
First things first, make sure the Sonos Arc Ultra is connected to your TV via the eARC HDMI port. Are you using the Sonos supplied HDMI cable or a different one?
Do you have several remote controllers or just the one for your TV?
If you’ve not done a manual remote-control setup via the Sonos App then there is a troubleshooting step you can do to figure out if it’s the TV changing the volume on the Sonos Arc Ultra somehow:
- Turn off your TV and unplug the power cable, wait 2 → 5 minutes. After that, initiate music playback from the Sonos App and check if there are any volume changes.
It is important to note, when you Submit Diagnostics, a screenshot of recent events on the Sonos system are being captured. If you Submit Diagnostics within 5-10 minutes of the issue occurring, it is easier for our Support to investigate, whenever you reach out.
I had a look on your relevant to this issue case with our Support and the diagnostics submitted there. I can see CEC commands for volume changes as much as Sonos Arc Ultra touch button volume change commands, but I do not know if this is happening on its’ own or if you are doing these actions. Your best course of action after trying the above and the issue still appears would be to once again reach out to our Support Team, informing them about every troubleshooting step you’ve done so far.
It is driving me mad - and sounds very similar to the issue here so I’m starting to wonder if there is a hardware issue:
The issue mentioned in the thread you shared is quite different, affected by the microphone of the device, making the audio ducking every time it did activate.
I hope this helps and feel free to reply here with any update you might have.
