Not really enough information provided to have a terribly valuable response. I’d be looking at the wifi interference FAQ and for sources of interference between the speaker the mini sub is bonded to, and the mini sub itself. But for better and more valuable input, 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 phone folks, they have tools at their disposal that will allow them to give you advice specific to your Sonos system and network.