Hey there heb147,
I apologize about the late response on this thread, thank you for being patient! Were you able to fix that Surround Sound issue? If not, I'd be happy to look into this. If you are able to do so, we would like to be able to isolate the issue further by having you connect to another soundbar using the same HDMI eARC connection. If the same issue occurs on this second soundbar, would you be able to submit feedback via the Google Home app with logs enabled? That way, our engineering team can investigate further. If you would like, we could also look at replacing your device if you believe it is defective, you would just need to either fill out this form, or get a hold of Chromecast support.