It may not be your WiFi, although it’s hard to understand how you could be certain of that unless each device was wired, but it could be network issues. 

Try unplugging all Sonos devices from power. While they are unplugged, reboot the router. Only once the router has come back up should you plug back in the Sonos devices.

If that doesn’t work, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis. 

Perfect ill try that. Thank you