I'm having a similar problem to an earlier post but with a MacBook Pro and a Sonos Roam at the moment. The Spotify app on Mac works fine without connection to Sonos. With the connection, however, the app plays one track and then will play another before stopping altogether. When it's playing the second track, it looks like it's still playing the first one. I did a hard and complete reset of the Spotify app per the solution on the other thread, but it didn't work.
All ideas welcome and thanks for any help you can provide.