If I had a nickel for every time someone claimed their “network is bulletproof” and it turned out to be their network, I could buy an Arc with Sub and surrounds.  So let’s drop that nonsense and deal with some facts.

Your symptoms are classic indications of duplicate IP addresses. These often show up after an update or power outage because a reboot requires the device to request a new IP, and the router, having lost track of current IP assignments, issues an IP that is in use by another device.  To cure this, do the following:

Reboot/power cycle your devices in the following order:

Modem
Router
Switches or hubs
Wired Sonos units
Wireless Sonos units
Computers/printers
Wireless devices - phones/tablets etc.

Allow each device to come back up before proceeding to the next.  Note you can prevent this from happening again by reserving IP addresses for your Sonos devices in your router setup.  See your router manual for instructions.

Note: I’ve been helping out here for going on a decade and a half, and I can count on one hand the number of times the above advice didn’t work, especially the reserving of IP addresses.  

Follow this advice. I don’t have such issues from one year to the next. I should say “one decade to the next”, but not all of the units are ten years old.