Steve,
I don’t think Sonos would write/delete anything from the local library - access is usually a ‘read-only’ permission. Just to be sure, go into your NAS settings and set the share to ‘read only’ - my thoughts are the ‘thing’ repeatedly deleting your tracks lies elsewhere.

Do you perhaps have some ‘schedule-based’ software in place that keeps the library in sync with another instance of the library stored elsewhere on the LAN, such as on a PC for example. If so, I would perhaps look closer at anything running on that PC.

A malefactor who does not share your exquisite taste in music?  In any case @Ken_Griffiths suggestion is sensible, especially if you have Remote Mirroring / rsync with nsomewhere] (which the 320 does support).  You can also look at system logs on D-Link NAS’s, but they are more oriented to outright failures, not regular operations.

P.S.  Be sure to report back here what caused the deletion -- this one deserves to be indexed!

Sonos just doesn’t write or delete files, on anything external to its own devices. It has the capability to read files outside of its own system, but can’t alter those files. Your ‘library’ for Sonos is a data file that exists on each Sonos device, which points to the location of the actual files themselves. 

Hi Guys,

Thank you for your prompt replies, I agree with all, I can’t see anyway that anything could delete the files let alone Sonos, I’ve just removed iTunes from my PC as I’ve just read somewhere that iTunes can remove non Apple purchased Music. I dont normally use iTunes but its on a Macbook I recently purchased and the Music Folder is pointing to my NAS\Sonos Folder.   I will remove the source on the Macbook and hopefully that might be the culprit. Weird thing is its been fine for years, maybe its something recent from Apple. I’ll keep you updated.

Steve

Pretty sure the issue won’t be Music (formerly known as iTunes), 95 % of my library was not purchased through Apple, and none of it has been erased….and in fact, most of it has been ‘matched’ in the Apple universe. 

It’s not entirely an ‘unheard of’ issue:

https://discussions.apple.com/thread/8189516

https://www.makeuseof.com/itunes-deleting-apps-music-library/

https://www.tunefab.com/apple-music/stop-apple-music-from-deleting-songs.html

Hi All,

Its been a good few days now since I removed iTunes from my Windows Desktop and deleted the link to my NAS Library in Music on my MacBook. All of my Media/Music is still intact on my NAS. This leads me to believe that my Music was being deleted by iTunes, I just cant see that the deletions could have been anything other than iTunes removing any non Apple purchased Music. 

Thank you all for your input.

Steve