I’d suggest the next time that happens, you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. That should give Sonos hard details as to what is happening, I suspect.

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.

Conversely, since no one else has yet reported this, it may be a download / corruption issue, just on your device. I’d be tempted to delete the file completely, then download and install a fresh copy from the Google store, making sure to ‘Connect to existing system’ when prompted. 

Thanks for your advice. I contacted Sonos support. They suggested me to uninstall + install app Sonos again + clean local data + star app Sonos looking for local system. Eventually it seems working properly. Once more a “clean installation” ( old time it was rebooting a system ) does work !