sonos roam volume issue

That’s odd. Why just Spotify, and nothing else? Sonos receives volume information from three sources in this case, through the controller, through the physical buttons (if they’re turned on), or through Bluetooth. 

I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. Don’t post the resulting diagnostic number here.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution. At the least, they should be able to see where the volume change is being sent from.

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.

If the volume is turning down by your phone and not in the Roam, the you may want to check your phone apps or something in Spotify that is doing this.

That’s odd… as was voiced by ​@Airgetlam. Assuming the device in question is yours and not a friends…
 

1. Does the volume drop at any distance between your speaker and your device?
2. Also have you updated your speaker and your device?
3. I must assume you are using the Spotify app otherwise why not send the music via the Sonos app over WiFi?
4. If using the Spotify app try signing out, delete the app and reinstall it.
5. Just to clarify…Which Roam is it…Gen 1 or Gen 2?