Have you force closed the controller?

If this does not resolve the issue, uninstall the controller and install a fresh copy. As you install the fresh copy take care to join an existing SONOS system, do not setup a new system. In my opinion it is too easy to click on the wrong entry at this point. Nothing critical is stored in the controllers. All of your music services, SONOS playlists, etc. will be preserved.

Refrain from Factory reset without further consult.

Great advice. It was intermittent. It seemed fixed and then it came back. I uninstalled it and reinstalled it one more time and it worked for the most part. TV surround works great but the system does not show up in my list of available speakers? All other 27 speakers work perfect but that one now? 
 

by the way, thank you. 

Reboot the surround system. I would power OFF all of the surround units, then reboot the soundbar or AMP first.

Is this a mostly wired or wireless system? Is the surround room wired?

I’ve had similar problems on past updates, assigning Static/Reserver IP addresses for all my Sonos followed by a Sonos power-down, router reboot, and powering up my Sonos - wired first - fixed the update and power failure recovery issues permanently for me. 

I’d be tempted to look in to line conditioners for the router and the Sonos devices. The situation suggests something that is messing with the OS on either/both, and I’m guessing some sort of over/under power situation.