This is usually indicative of some sort of wifi interference , where the speakers are having trouble maintaining a connection to your local library. You might find it reacts similarly with streaming content, but it varies.
I’d start with a simple network refresh, by unplugging all your Sonos devices, as well as where your local library is stored, be that a PC of some type, or an NAS. Then I’d reboot the router. Wait a couple of minutes for the router to recover, then power back on all devices, including the Sonos, and where your local library is stored.
But, while I do think this will resolve your issues, if it doesn’t, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, their lawyers get sensitive about GDPR.
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.