Would seem odd to be a WiFi issue, the data lives on the speakers, and is only shown in the controller. If unit appears in one, it should appear in the other. The ability to ‘save’ playlists is currently rolling out, although it appears not everyone has been ‘activated’ yet, but have you updated since Monday last week?
I would be extremely tempted to disconnect that Android controller from the Sonos system, reboot the Android device, then reconnect it. If that doesn’t make difference, I’d submit a system diagnostic from both the Windows machine, and the Android device, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here, they 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.
