arc ultra

Rather than relying on a crowd sourced probability, I would recommend that you submit a system diagnostic within 10 minutes of reproducing the issue, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

So you’re saying it’s not occurring on all programs. Is the volume drop consistent with specific programs such as always with program A but never with program B?

So basically it’s an ongoing problem, not constant but is more noticeable on music or live sport where there are various volume input such as commentary and crowd noise or on 

music where there are vocals and instruments.

For some reason the soundbar seems to highlight one or the other without a equal level.

If you watch the Sonos controller's Room screen does the signal type shown there change when the sound does?

If you play the same content again does the sound change in the same places?

Do you have any voice assistants enabled?

The diagnostic and support call may be the most effective option. Make sure to,capture the diagnostic within a few minutes of the problem. Sooner is better, 10 minutes is likely too late. Sending several wouldn't hurt, note the numbers and 2hat was going wrong for each. 

You might also want to try it with a different TV, if you have one... and I’d also check the TV's audio settings... I recall dealing with this on an LG TV in the past... and with a 5-year-old model, there could be a firmware issue somewhere (I don't use LG myself).