Hard to tell from the information provided. I’d start with a network refresh, by unplugging all Sonos devices from power, then rebooting the router, and giving it a couple of minutes before plugging back in your Sonos devices. I’d probably refer to the  wifi interference FAQ, too. 

But if none of that changes anything, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.

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 Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.