Spotify connection to Sonos very intermittent

[the_goon]

Plan

Free (as I'm trying to solve this issue first)

Country

UK

Device

Google Pixel 3

Operating System

Android 10

My Question or Issue

Hi
I'm new to Spotify, as I'm looking for a replacement to Google Play Music which will end this year some time.
I have on my network 3 Sonos speakers. I can cast to any of them perfectly fine through the Sonos app on my Android phone (Pixel 3), and perfectly fine through the Google Play Music App. However when using Spotify, the Sonos speakers do not appear on the list of "Devices Available" 100% of the time. Sometimes I'll get them all listed, other times just one. Most of the time, none of them are listed as available.
When they do show up on the list, I can play to them just fine. Does anyone know why they aren’t showing up consistently?
When they don’t show up on the list, I can immediately go into the Google Play Music app and connect to them through that first time, every time.

I have tried rebooting my router, resetting my Sonos speakers, moving my Sonos from a wireless to wired setup, but none of these made any long lasting effect.

Thanks

[the_goon]

OK. I think I've narrowed it down.

Spotify Connect doesn't connect to any of my Sonos speakers if my phone is picking up my 5Ghz network (my router is dual band). If I'm on the 2.4Ghz network, it seems they all show up.

Spotify Connect is the only app I am own that has a problem with a dual-band router (both the 2.4 and 5Ghz bands are the same SSID etc).

Anyone know why Spotify Connect can't see the Sonos speakers (which have to be on the 2.4Ghz network) when my phone is on the 5Ghz network?

[leowinterde]

Hello,
after weeks of struggling with the spotify <-> sonos connection and hours of testing today, I can reproduce this fault.

This error only occurs on my Pixel 4 XL with Android 11. Deactivating the 5Ghz wifi helps, but is not a real solution.

Another solution is to connect my sonos beam via. ethernet and remove my wifi network in the sonos app, so the sonos system is using its 'mesh' wifi network over all the other x6 sonos products that i own. Yes its loading/'blocking' some wifi channels but that is fine for me - sure not great.
My network 2.4 & 5Ghz (basic unifi setup with multiple APs) its blocking any isn't blocking anything specific though.

Greetings