After every two or three songs (on Apple Music+ in the Sonos app) the Atmos badge still disappears around 20 seconds into the song. The music reverts to normal stereo.
I have frequently called customer service and gone through all the diagnostic steps, restarting etc. I also created a topic on this community page. Sadly after more than 6 months nothing has changed. The topic was even closed for further discussion. I know there are quite a few other Sonos owners with exactly the same problem, and wonder when there finally will be a solution to this extremely irritating and embarassing (when friends come over) situation.