It may benefit to power off your router, tv and Sonos speakers. Then when you power up again after a few minutes, they are all running in a stable state. Then see how it goes.
 

You might also be able to set up the tv remote as the volume controller.   https://support.sonos.com/en-us/article/tv-remote-requirements-for-sonos-home-theater-products
 

I will randomly get system not found when I launch the app. I close the app and reopen it and it's good. I've never had to power down speakers.

Thanks both. I’ll try as suggested and see how i get on.

I never had any issues with the old app.