I’ve found that Mosaic is occasionally “forgetting” the contents of playlists I’ve created. Just now when I fired up the system the playlist names are there but the contents are random tracks and not those that I created.
And, yes, I rescanned the songs and playlists on my Melco. I also, completely shut down the Bartok. No help. My most recently created playlists (created yesterday) are intact but all the ones before are garbage.