Best answer by melvimbe
This sounds like IP address conflict. After your speakers reboot (which will happen during an upgrade) the router assigns them new IP addresses. Some routers have a tendency to assign IP addresses that it already assigned to other devices in your home, creating conflicts.
To resolve, unplug your Sonos speakers, reboot your router, then add back the Sonos speakers. For a more permanent solution reserve IP addresses for your Sonos speakers in your router's configuration.