Hi. My System (only 15 devices) still works fine. 

Which mesh system? Is your ISP router still used in your network? 

Are any of your Sonos devices wired? If so, what to?

(We need to find the actual cause of your issues,  which is very unlikely to be anything to do with the update. )

I am using the TP Link Deco wireless routers. I have disabled the wireless router from Spectrum and just use it as a modem. I have one of my Sonos connect amps hardwired.

Bill

 Mine work fine.  Xfinity network with one extender.  All devices with reserved IP addresses.  App is still quirky.

There is a good chance that because you have a Sonos Connect amp hardwired that in addition to your Deco mesh, you also have Sonosnet running in parallel. *Personally* I think there could be some correlation between Sonosnet and a worse experience on the new stuff (ignoring all the functional dropped whatsits). 

Even if you initially set the system up on WiFi, plugging something in via Ethernet will re-introduce Sonosnet, and when you do any updates and stuff reboots it silently picks it up, or tries to. 

I know it’s a PITA, but power down all Sonos speakers bar the ethernet attached Connect. *if* that appears in the new App, disable WifI for that connect and reboot. Verify that it still shows WiFi off. Then restart each additional WiFi speaker and verify it comes online. 

That *should* mean you are on the Deco mesh only and *may* improve things but there’s no gaurantee. 

I also use TP-Link Deco routers. If it’s any help my configuration and story is as follows:

TP-Link, 3 node Deco XE75 using the 6GHz band for backhaul. Installed about 6 weeks ago so with all the issues of recent app and firmware to deal with. Took a few factory resets on a couple of Sonos Ones (Gen 1) to get them connected but 11 other devices connected OK. I use the Deco in router mode, ISP supplied router is in pass thru mode and it’s WiFi turned off. With the Deco software I have each Sonos device tied to a specific node, with static IP, and with seamless roaming turned off on all except a Roam. This reduces the risk of Sonos devices switching nodes just because the speed is slightly better on another node. Stability is much better than my old WiFi 4 setup but still not 100%, have a Connect 2 that drops out periodically, typically a network scan for interference or possibly a router reboot fixes it. If not that, then connecting it by ethernet usually lets things settle down - at present it’s connected via WiFi. 

Home WiFi typically has 35-40 clients connected and we have two Zigbee hubs, both on channels to reduce any 2.4GHz interference. 

App issues remain a problem, no idea how many times I’ve reinstalled it. System is still not fully stable, get an issue of some kind most days but it has been getting better with each successive App and firmware upgrade.

Yes, there is always hope.

My system has worked since the May update, I don’t have any Sonos devices hardwired, I ‘pulled the plug’ (ethernet) a year or so ago. You may want to consider discussing this with Sonos Support, if your TP Link WiFi is stable, if you do decide to reset, you will loose Sonos playlists/favourites etc (if you have them)

https://support.sonos.com/en-gb/article/connect-sonos-to-a-new-router-or-wi-fi-network

@Iain59

My TP-Link M5s are in AP mode, rather than router mode, with the ISP router handling all DHCP allocations. WiFi is off on the router and on for the three nodes of the mesh. My Sonos system is working well. 

Seamless roaming also off for the Sonos speakers, like you.

Worth trying the mesh in AP mode to see if that works?

100% The benefit of Sonos was that you didn’t need a networking certification to set it up. If you had problems support could tell you exactly what the issue was in 10 minutes. This is no longer the case. 

@Rhonny 

Have tried both, no difference in overall stability between the two but I lose the XE75s QoS capability in AP mode. Stability is now much better than it was and most issues I have are wifi related or the App throwing a wobbly.