The Sonos Desktop app has no actual way to create an Apple Music playlist, deliberately or accidentally. There is no API to do that.

Maybe it is displaying them twice? (Looks like it based on the screenshots).

Maybe the itunes xml file is someone duplicating them?

What do my Windows apps (see profile) show for the same items?

It’s pretty clear there is some duplication happening in the desktop app but I am unable to locate where, why and how.

You probably have another copy of the iTunes playlist somewhere else that Sonos can access.

Often it is in a Recycle Bin.

Try renaming it and seeing if one is renamed or both….

I’ve not touched iTunes in years, I only use Apple Music. When a service is added to Sonos, it is auth’d to the same account as Apple Music, which only has the individual playlists, not duplicates. That is the same email I sign in to Sonos with and is my only and primary Apple Music email address. There’s nothing in my iTunes library anyway, almost forgot how to even use it 

No duplicates in iOS Apple Music either. Also, the playlist duplicates only happen in the Playlist sub menu on Sonos IOS, on the Sonos Home page (pinned collection), there are no duplicates.

None of the above addresses what I've mentioned though.  Where is the library? On a PC or NAS? Maybe there's a backup folder or similar being indexed by Sonos.  Wherever Sonos is looking for the library, do a manual search on there for the library file (xml still?).

It’s not a local library, it’s simply playlists created directly on Apple Music and adding Apple Music as a service.

Aah, OK, apologies. Is the ‘Music Library’ option empty?

But also, as above, if you temporarily rename a Playlist do both versions change name?

I'm not an Apple user, could there be some other Syncing going on to somewhere that contains the same content - i.e. the duplicates?

Also, if you add a track to a Playlist, does it instantly show up in the duplicate?

Music library is mapped to a local NAS but rarely used. In answer to the question, do they all update, yes, they do:

I am wondering if this has something to do with sharing the Apple playlists with other users. Does Apple Music reflect that to Sonos as a duplicate instance, to be honest that may well be the $64,000 question. I am going to delete the playlists from my other half’s phone later and see if that removes the duplicates.

As I said before, try either of my Windows apps for Sonos and see if they show there. (Not the Apple Music app). If they do, its an Apple Music service problem. If they do not, its a Sonos Desktop app bug.

I am not sure what you mean by “my Windows apps”, I have shown above that the Windows Sonos Desktop App clearly shows the duplication that does not exist in the Windows Desktop Apple Music App. Moreover, I have shown the same duplication exists in the IOS Sonos App but does not exist in the IOS Apple Music app, so everything points to a Sonos bug or misinterpretation of information from Apple Music.

Having said that, I believe you may also be referring to the Sonos browser app (https://play.sonos.com/en-us/web-app) so also had a look there and the duplication does not exist:

So it must just be an issue wiht the Sonos Desktop App and Sonos IOS App..

I removed it, deleted the x86 program files folder and reinstalled, duplcates still come back. Deleting shares from another users phone had no effect.

I write Sonos apps - see my profile. Two of them run on Windows.

I think I’ll stick with OEM free apps, thanks. I can see you pitched in on this Reddit thread also a year back, seems that was never resolved.

https://www.reddit.com/r/sonos/comments/1axcvln/anyone_know_why_my_sonos_app_is_doing_this_with/

He isn't pushing his Apps, he's using it to try to Troubleshoot where the issue is.

Although OEM apps are still lacking in functions that they could do 12 months ago that are still supported in non-OEM apps.

Have you always had duplicates or have they appeared after a recent Update?

These duplicate playlists have been there a long time, I cannot recall when they started, I’ve just never found a fix for the issue.

I tried something else, I’m not sure what this proves / disproves but it had an interesting result. I created a playlist folder in Apple Music and moved my playlists in question into that folder. Then I re-added the Apple Music service via IOS. In IOS, the playlists are not duplicated within the playlist folder. Previously they were, see above.

In Sonos desktop, the ‘top level’ playlist section has changed but again, duplcating. However if I then go into the ‘Sonos Share’ folder, the next level down, the playlists are not duplicated.

As I said, I am not sure what this proves, but perhaps a new URL has been created and updated into the Sonos rest API (I assume that is how this works, I don’t know). No duplicates in Web app also.