Running iOS 13 beta 4. I have Apple Music but iCloud Music Library disabled. I have (or had) nearly 100 GB of synced music from iTunes. A few days ago, all my synced music suddenly disappeared, and all that remained was the music I've added in Apple Music. (I don't have iCloud Music Library enabled on this iPhone, but there is Apple Music in iCloud Music Library that I access from other devices.) I re-synced all my music back from iTunes. Then the same thing happened today. All my synced music disappeared, and all that remains is what is contained in iCloud Music Library, which is still disabled on this iPhone. These events happened randomly and independent of an iTunes sync. There is sufficient space on the iPhone (only half of the 256 GB were used when the synced music was present). I confirmed that the music is in fact deleted, as it is now free space. This had never occurred before, and now it happened twice in a handful of days. Has anyone else experienced this?