That suggests a network challenge, with your Sonos devices having difficulty maintaining a good connection to the source.

The troubleshooting step I would start with is a network refresh. Unplug all your Sonos devices from power (or power them off, in the case of the battery powered speakers), then reboot your router. Give the router a couple of minutes to come back up, then plug in (or power up) your Sonos devices. Give them a couple of minutes to settle in before testing. 

However, if this doesn’t clear the issue, 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.

https://support.sonos.com/en-au/article/understanding-the-network-details-section-in-the-sonos-app

 check the SNR  Signal to Noise Ratio of each speaker.

Well the network refresh is the default answer however to no avail since Sonos themselves broke the system with the crap app. Among the hundreds of other issues, totally self-inflicted. Don’t expect any improvement soon. Nothing substantial has happened since the flawed app got launched in May. CEO Spencer (who has yet to made himself redundant because of this shambles) posted a letter in July, so far empty words.