There really isn’t an ‘in Sonos’ data repository for the music itself. All Sonos does is build a track list of the data in your music library based on the tags it finds, but it’s just basically a text file that points to where your music is.
I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it.
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 phone folks, there are more options available beyond just the diagnostic analysis.