You’re convinced it isn’t your home router, many of us are confident it is, with either wifi interference impacting the ability to reach your speakers without issue, or possibly a duplicate IP address issue, again on your router. My opinion, based on your post, is the latter, but it could easily be the former, as the symptoms could be the same.
Why are you adamant about not restarting the router? If it were me, I’d want to try anything to fix the issue. In your situation, I’d unplug all my Sonos devices first, then reboot the router, waiting a couple of minutes for it to come back up before plugging back in. If indeed that worked, I would expect it to be a temporary situation, any router that has given out bad IP addresses once could potentially do so again, so I would read the router’s manual to learn how to set up reserved IP addresses, and do that at least for all my Sonos devices. I’ve done it on my router for all my network devices, it is good network management. I leave the first 50 IP addresses open for floating devices, including guests, since I don’t use the guest network function of my router.
Sonos uses the network in a significantly different way than most devices, the Sonos speakers, in order to stream music, need uninterrupted access.
However, you can always submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
