Odd. I wonder how they ‘remembered’ the old network data. 
 

In any case, I’d follow the instructions in the new router - installation instructions FAQ.

I had the same issue.

Settings → Network → Manage Networks : Delete old networks

You may need to re-register 1 or 2 speakers

This is a real disappointment I'm sure to everybody who's experienced it. For me, a residential integrator who installs systems and manages several hundred homes, some of them with dozens of Sonos's, this bug is something that can take a system which was set up and working perfectly and turn it into one which causes spanning tree issues and your network will flap on and off causing you to drop calls, video meetings, block your internet connectivity all together, and unfortunately for someone like me who runs a business, accrue a whole lot of expenses driving around trying to figure out what the problem is.... Finding that Sonos has reverted a setting which was set specifically in their software, which makes us and Sonos look like jerks in addition to causing the frustration on the part of the owner.

If you guys at Sonos can't fix your spanning tree issues you at least need to fix your Wi-Fi setup so it doesn't revert to a broken POS. 

Normally I wouldn't be so hostile, but I am driving back from a half wasted Saturday trying to fix this for a client whose network went down in the middle of a VC call yesterday because of you. Reputations have to be tended, and you may have a big market share but you're slacking. From my perspective your product is a gamble.

Fix It

Maybe Starlink WiFi went down briefly and since the former WiFi was still defined, SONOS switched back to the old WiFi.

On my system there are two WiFi’s. One set is actually a mesh. All are on the same subnet. The SONOS system is free to use either WiFi and there can be a mix. (Meaning some SONOS units are using ‘A’ while others are using ‘B’.) If one WiFi goes down, all of the SONOS units will switch to the still operating access points. And the SONOS units are free to use 2.4 or 5GHz as they like.

If there is a risk that a SONOS unit could use the wrong WiFi, be sure to remove this network from the SONOS network settings.

Did you supply any data to Sonos so they could figure out what had occurred, and ‘fix it’ for you? Or are you just complaining randomly on a forum, without any data to back up your complaint?

Thanks Bruce. I am complaining, yes.

As it turns out, these forums tend to get more attention from customer service and engineering then actually trying to electronically submit anything and get it fixed. That said, this is something that we have seen happening on several systems and there is most certainly a pattern. Unfortunately due to the nature of having to fix problems with other people's systems in a timely manner, we are not able to sit and wait for Sonos to use our time and our clients systems as a debugging venue. The spanning tree problem is something that Sonos has never addressed adequately since the inception of their devices riding on people's networks and not using zp net. Real facts. 

If it makes you feel better I most certainly can submit system diagnostics the next time this issue pops up as it most certainly will, but given how long this has been problem for Sonos I would not expect anything until people really start complaining and/or choosing other better options. 

Spanning trees are obviously only relevant when in SonosNet mode, and instability is more likely to arise where multiple units are wired. Basically, Sonos’ modified STP can get into a tussle with whatever’s running in the backbone. The latter could well be the more modern RSTP, and the differences in path costs, convergence times, and so forth between STP and RSTP can result in unintended consequences. 

IMO we’re unlikely to see much, if any, attention given to this area by Sonos. The latest Era units can’t use SonosNet at all, and this is a trend that’s likely to continue. SonosNet was essential in its day, but its bandwidth is low and its performance is now well and truly eclipsed by modern WiFi 6 meshes. In fact Sonos is most likely to ring-fence the SonosNet code and post a warning sign at the entrance, for fear of causing regression. 

It would make me feel better. Simply a complaint, especially as Sonos could be having difficulty replicating this issue internally, might be helpful. It’s also a pretty random, and extremely rare bug, based on what I see in this thread. I’ve certainly never experienced it, but then I’m a single point of reference, and only deal with three systems at most. Providing data to an engineer works wonders. I’ve often asked my engineering staff to fix a bug, and the first response is, ‘ how do I replicate the issue’. 
 

Given the infrequency of this, and the movement away from SonosNet, I do agree with @ratty , it seems, especially lacking any replication data, for it to get any significant attention, even given the rant you’ve posted. 

True, somewhat, although this is not just a Sonosnet issue. If it was then it wouldn't cause spanning tree on the lan WHEN THE WIFI ENABLE/DISABLE SETTING RANDOMLY REVERTS TO ENABLED which is not something I can advise on how to replicate but assuming Sonos has a lab with hundreds of devices and people paid to use it, they would be able to catch it. 

And this is not infrequent, I've got 3 systems in the past 3 weeks running on updated and managed networks that have reverted on their own, but since stp takes down the WiFi port when the event happens, the network is rendered useless to the end user even if the gateway and some segments are still unblocked. 

I encountered a Ubiquiti update that wrecked STP for SONOS.

This is surely all to do with SonosNet. The “WiFi” enable/disable switch has nothing to do with WiFi at all. It enables/disables SonosNet wireless on the device.  

If the setting is somehow re-enabled then it’ll (re-)establish SonosNet wireless pathways that could potential cause loops or, in the case of an STP/RSTP battle, bridge wirelessly (and slowly) across the wired backbone.

FWIW in 16 years I don’t think I’ve ever seen a device take it upon itself to re-enable its radio in normal operation.

At the point when it’s actually being disabled via the controller it may revert within a minute or two if it decides there’s no satisfactory network pathway back to the controller. This is a safety precaution to avoid a device marooning itself. Also, the device will want to see a direct wired path back to the STP root bridge, rather than be daisy-chained.

Of course if the device is put through a factory reset it will also re-enable its radio.

Welp that's odd, since as I have now removed the Home WiFi said and logging from Sonos, in addition to the per device level disabling of WiFi, they have not reverted to Wi-Fi enabled. 

Which means no portable speakers for these owners.... Fine by me. So long as the Sonos stack doesn't kamikaze the network anymore. 

Just had the same problem. I recently moved my whole house to a new ubiquiti router. After a month my playbar suddenly just jumped back on to the old network. I don’t know how considering it was reset and that network was not in the list of known networks. Where are these being stored? 

This data is stored on each speaker, and not in the controller. 

We've had several more systems go down over the past few months. I'm over it. Blue sound is better quality and I can stand to do without the problems..

In my installation the SONOS units have choice of two WiFi networks. One is a mesh and one is the ISP’s Gateway. Both are on the same subnet. When I check the players, in some cases the SONOS system will be split between the two networks, in other checks it will be all one or the other. The controllers can also flip between networks. During a WiFi hardware update the updating WiFi will shut down and the SONOS units will flip to the other network. I deliberately setup to allow this WiFi choice.

Typically, when adding a mesh or replacing the Gateway you’ll end up with separate WiFi networks. You must make sure that SONOS and the controllers are always on the same subnet and that there is only one router. Check to make sure that the unwanted network is not listed. Also make sure that your controllers are not using the wrong access point. In addition to the two home networks, I have an office network defined here too because I may occasionally take a unit to work. The traveling unit will seamlessly connect at work.