I have ripped a lot of Allman Brothers, and Sonos has put it in three places, "The Allman Brothers" "Allman Brothers" and "Allman Brothers, The," and I wanted it to be all in one directory. So I pulled up the Allman tracks and made sure the Artist was consistently named Allman Brothers, The. I only had to tinker with about 10% of the tracks. After I finished, I went back to Windows explorer and many if not all of the tracks were no longer in the folders I had ripped them into but were just all grouped together below the folders. So I went to cut and paste them into the right folders and many of the tracks are now missing, but hopefully weren't deleted. Any help would be appreciated. Thanks.
Mp3tag is not automatically moving files if you only change the tags or the filenames. Can you check if the Sonos performs some magic there?
Also, try to use Windows search to find the now missing files. My guess is that also Sonos is not randomly deleting tracks.