What router are you using? Which speakers are currently wired to the network with an ethernet cable? Do you have WiFi enabled on all speakers? Have you tried changing the SonosNet channel under the Network settings in the Sonos app?

Hi,
The Beam is wired to the router, and wifi is enabled for the two back infills (ones) plus the sub also wireless.  Have tried all three channels in the network settings.
The router is a Unifi unit.
Still does not explain why the 2 three’s keep disappearing off the network either.  
Currently, rears keep cutting out, not showing as connected in the app, but still playing audio (intermittently) and can mute the audio…  Makes no sense at all, but thanks for the suggestions.

It seems like many Sonos users experience issues with UniFi.

This might be helpful:
https://community.ui.com/questions/Getting-Unifi-and-Sonos-to-play-nice/5d3c8cf2-5d11-4aea-ab4c-977736749159

Folks have reported getting Ubiquity gear to work BUT getting it to work with Sonos means setting it to be compatible, not changing Sonos settings.

I found the compromises required to be more than I was happy with. I bought Ubiquity gear for all the advanced features and capabilities, not to dial it back to deal with other hardware not capable of the newest options.

For me the simple route was to wire one Sonos (initially, ended up wiring more) as you have, and then when all Sonos switched to SonosNet / wired mode removing (did you do this step?) the WiFi credentials from the controller. Putting the SonosNet on one of the three clear channels and my WiFi on the other two (no auto-switching) gave me very reliable connections for my Sonos gear and the best possible connections for my other WiFi toys.

Only other tweak I’ve needed was to assign static/reserved IP addresses to my Sonos to survive power outages, updates or just unplugging and moving them.