Almost certainly a network issue, most likely with the router not properly reloading the DHCP table. I had a similar issue many years ago with a router that wouldn’t recover properly from power surges and outages, I resolved the issue by setting up reserved IP addresses for all network devices in my router. That data appeared to remain persistent across all power interruptions, and I stopped ‘losing’ access to my PLAY:1s and PLAY:3s. 

Thanks Bruce 

I think I understand what your saying but surely wouldn’t all the Sonos kit suffer form same problem ? Why would only 2 of the 5 units have this issue ?

Thanks

Dave

Because those two units are having either wifi interference or duplicate IP address issues? Neither of those potential problems would hit all units simultaneously, while a software issue likely would.  Testing is the key here, and frankly nothing is better than a diagnostic, submitted to Sonos and then followed up with a call to their phone folks. The best thing is the hard data in the diagnostic to look at, something those of us who are not Sonos employees don’t have access to. 

And frankly, I could be wrong. I’d give myself a 98% or 99% chance of being right, but a diagnostic could point out something out of the ordinary. Unlikely, but not impossible. The joy of diagnosing network/software via text discussions :)

Get a better router. DHCP is a basic requirement to get right, if that doesn’t work correctly then chances are not good for other, basic router features.

Meanwhile rebooting the affected Sonos devices a minute after your router reboot should suffice as a workaround, but who has time for that?

It isn’t the quality of the router, I have had the same issue with several very good quality home routers and three small business class routers, the last a week ago on a Netgate SG-3100 and pfSense firmware.

Several years back I spent a lot of time testing this situation and there were no indications of any issues in the router’s system or DHCP logs. I don’t have fancy network monitoring gear but I did do the basics possible from a Linux system and it found no issues either.

Last week, after several hours of playing around with this last go-round I did the basic power off all Sonos, then a reboot of router and controllers. Followed by powering a wired Sonos, then I did each additional room one device at a time, again any wired ones first. That brought the system right back up with no issues. Before the power-cycle/reboot devices were coming and going, functions wouldn’t work then they would, as would music.

As soon as everything was back up, working properly, I assigned static/reserved addresses to all my Sonos gear and did another power-cycle/reboot to get all on the new addressing. No problems since.

It is very frustrating, I can’t find any sign of duplicate IPs, a MAC associated with an incorrect IP or anything else going on on the network to explain the issue. I’m hoping the instability on power cycle or after an update is an issue stemming from the antique version of Linux Sonos is running and the associated ancient network software.

I can’t find it, I can’t help fix it, but at least I know how to work around the problem.