Playing from Spotify starts on all speakers for a split second, then goes to just one

Interesting.  I think you were seeing them change channels because they were actually changing APs as the APs applied the update to only 5 GHz for that SSID.  This got me looking into the channels they were using.  The APs do change channels occasionally on 5GHz to avoid radar on DFS channels.  I live close-ish to an airport.  I have no idea if that’s what causes that or what, but it does happen and looks to also have happened right before the last diagnostic.  

I also noticed/remembered that I locked these to a specific access point to try and troubleshoot this either while on the phone or before talking to the first rep I spoke to.  During that call I believe he had me enable IGMP snooping.  I’ve read a lot about this and how multicast enhancement works on Unifi since starting this thread and believe I now understand how that works where I didn’t before.  When I first set up this system on the SSID you see now, I had all sorts of issues like this.  Very first thing I thought to try was moving them to the 2.4GHz only SSID, I never turned off multicast enhancement on the combined SSID.  Then the rep had me enable IGMP snooping.  And now today I’ve disabled multicast enhancement on the combined SSID.  

So now that I’ve unlocked them from the specific AP that I chose, they’re all over which is fine and all connected at 5GHz.  Spotify app and Spotify through Sonos are working instantly.
 

Diagnostic # 582724345

This leads me to believe that I probably artificially handicapped the system by locking them to a single AP and locking them to 2.4GHz, when in actuality IGMP snooping and multicast enhancement may have been the culprits from the get-go.

Unless you see anything else, I’ll run this for a few days and see how it goes.  I’ll also try and get a packet capture to track down the multicast flooding you’re seeing.

Appreciate the help!  And very much appreciate the willingness to work with me even though my setup is probably more complex than most.  Phone rep was a little out of his terrority for this.

Hi @forebittclash 

Sonos uses multicast frequently, so anything that interferes with the transmission of it will cause problems. It certainly sounds promising now that Multicast Enhancement has been disabled. Yes - let’s see how it behaves long-term.

Having all your speakers on one Access Point can certainly simplify matters for Sonos, but on a well-configured network, it shouldn’t be a prerequisite, and it does of course prevent each speaker from connecting to the AP with the best signal for it.

I would not expect aeroplanes to interfere with your network, but the airport’s radar may be a different matter - a Google search reveals multiple frequency bands in use for various purposes, but they are all outside the ranges used by WiFi. The power of the transmissions is what would concern me the most, at 25kW. There isn’t much you can do about this, however, short of moving home.

To be honest, with the multicast flooding appearing to be largely confined to short moments, I would test things as they are (with Enhancement disabled) for a while before digging into finding the source of the flooding - it may not be necessary to do so after all.

You are most welcome - especially after spotting a typo that had been on my Pi-Hole article for nearly a year! Backscratching is good!