Hi @nantwichguy
Welcome to the Sonos Community!
It seems your Sonos system is having a bit of trouble remaining connected to your Google Mesh - it’s trying to steer them to a 5GHz connection because they have 5GHz radios, but some won’t do so as they reserve their 5GHz radios for direct links (like your surrounds to your Arc).
As the Google Mesh will not allow you to split the 2.4 and 5GHz bands, we’ll need to take another path towards connection.
Please connect any one Sonos device (not a Surround, Sub or Roam) to your Google Mesh (or to a network switch attached to Google) with an ethernet cable and wait for about 1 minute. Keep the device 1m away from your Google node and router.
This device will transmit a private WiFi just for other Sonos devices which each device will repeat, creating their own mesh. The Roam will not connect to this network (SonosNet), but it will happily connect to 5GHz WiFi.
When creating a large group, it’s best to put the ethernet-connected device in charge of the group (selected first).
With the minute over, please check Settings » System » About my System and check that all speakers apart from the Roam report WM:0. Reboot any that don’t.
If you’ve had to move a speaker to do this, I recommend you test long-term (a week or so) and if you’re then happy with the performance but need to move your speaker back again, you may want to add a Boost to your system.
I hope this helps.