Do you have Simplink (CEC) enabled in your TV settings? Have you tried using a different HDMI cable? Do you have any other external media devices connected to the TV?

No other devices linked. The hdmi cable was tested with another tv and worked fine. It was run through a chase pipe so would be difficult To try another hdmi. Simplink is on

Disconnect the Amp from the TV and unplug both the Amp and TV from power for a couple of minutes. Plug them both back in but keep them disconnected. Be sure Simplink is enabled and run TV Setup under the Amp’s settings in the Sonos app. Connect the Amp to the TV’s HDMI ARC port when the app instructs you to.

Also be sure to turn off eARC in your TV settings.

So it’s only switching back and forth when I watch certain things such as Dolby 5.1 and Dolby logic. 

Sounds like CEC, which is perhaps enabled on your other HDMI connected devices, is stealing focus and/or the Arc is losing its TV connection and that in turn is causing the TV speakers to kick in - I would maybe try switching off CEC on those ‘other’ products (if relevant) and maybe try another heac supported HDMI cable between TV & ARC to see if those things sort the issue.

The only thing I have hooked up to the C1 are the Sonos amp in HDMI Arc.  It’s really odd. I haven’t had the issue on Hulu even with 5.1. But with Netflix and Disney plus it occurs more often

Have you disabled eARC in your TV settings?

I still think you should try another HDMI cable if possible.

Could it be Dolby Atmos programs?  It seems like those are the times the lg speakers and amp are fighting for control

It’s still only switching back and forth on certain Disney plus and Netflix programs and I think they are Atmos ones. There has to be a way to prevent this from happening