Apple Music is deleting Artist and Album folders from my hard drive

I have suspected this for some time but it is so random and I have such a large collection of ripped CDs on my hard drive it can be weeks before I notice folders are gone.

Last night, my wife and I were using Apple music on the Apple TV and she selected a song from her library (DiVinyls), which is from a CD ripped using Apple Music in ALAC format and stored in the Itunes media library on our NAS. When she selected it, a window popped up which said something about not being able to play it because of a syncing issue (I should have paid more attention to the notice) and now the album is gone from the NAS.

This is not the first time, as I said. I have had suspicions for some time and made sure the Mac Mini I use to rip CDs to de-select the option for iTunes (it is an old Mini) to organise the music library. However, my wife and I both have sync library selected in Apple Music.

I have noticed that it is not just albums that Apple is deleting, but also Artist folders. I recently had to re-rip my Radiohead collection because it had mysteriously disappeared. The NAS is not used for anything other than music and I am the only one who uses it.

I am going to turn off the option for Music to sync our library across devices. Are there any other options I should turn off to be careful? Or should I stop using Apple Music altogether to be safe?