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.

Thanks. Calling now.

For security reasons SONOS asks that users do not post diagnostic numbers here. In previous decades SONOS could not easily correlate diagnostics with a particular user and asked that the number be posted. This is no longer the case. You can edit your post to record, then remove the number. It’s likely that a moderator will remove the number.

Not sure the OP posted a diagnostic number? Just the version of their Android app?

I did. I removed it, thanks. 

Ah, gotcha. I didn’t see it ;)

The problem has returned. 

This is utter madness.