I’m not sure what you are experiencing. The typical complaint is that level can vary from track to track and this is caused by differences in the track recording levels. I don’t recall any previous complaints with respect to levels changing while a track is playing, however, some tracks, particularly classical music and some jazz tracks are very dynamic. Pop music levels typically don’t vary much.
An Internet news radio station would be a good test choice because the audio level will be very consistent, although some stations will boost the level on commercials somewhat.
You could take this up with SONOS phone support. First, submit a diagnostic after one of the Volume level incidents. If a PORT is having issues, they will usually leave data in the diagnostic.
