Playlists auto re-creating

This has been happening to me for a while, but it was usually only a handful at a time. I'd delete them, and everything would return to normal. BUT, after the iOS 9.3.5 update, I am getting exponential duplicates for EACH playlist. It's out of control, now.

I have tried turning off music syncing, but it keeps turning itself back on. It's driving me nuts.

iTunes may be doing this because iTunes sees a change to that playlist, on the iPod (or iPhone), that is not in the iTunes library. There may not be such a change, but iTunes see a change for some reason, so iTunes creates a new version of the playlist (with appended number) in iTunes library so that you can decide which one to keep.

If this is happening in error (there is no change to playlist on synced device), I would try setting iTunes to not sync that playlist to the device, and Apply the change, so that the iPod (or iPhone) no longer has the playlist. Then, set iTunes to sync that playlist again and Apply. See if that stops iTunes from re-creating the playlist.

Do you subscribe to Apple Music or iTunes Match (or both)? If you do, are you actually syncing directly from your Mac's iTunes music library to the two iOS devices, or are they accessing music (including music playlists) from your iCloud Music Library (provided by your subscription)?

Because the 1-appended playlist has fewer songs, I'll go back to my theory that when syncing, iTunes thinks the playlist has changed on the device (even if it did not). Therefore, it gives you the changed version (with "1" in name and fewer songs) so that you can decide which to keep.

I'm assuming you use automatic syncing. Go to the device's Music settings screen (with the Sync Music checkbox) in iTunes. Do you have this screen set up to Sync Music (checkbox) with Selected playlists, artists, albums, and genres? Or is it set to sync Entire music library?

I used confusing terminology... Automatic syncing is what happens when you have Sync Music checked. iTunes automatically syncs the device when you connect it.

Sync Music is ticked and Selected playlists, artists, albums and genres is also ticked.

So, that means you have that problem playlist selected (checked) on that screen, under Playlists, correct? Try unchecking that playlist there, so that it no longer syncs to the device. Click Apply.

After syncing this way, using the device, confirm the playlist is no longer on the device. Then, go back to the device's Music settings screen in iTunes, and select (checkmark) that same playlist again. And click Apply.

See if removing the playlist completely from device, and then adding it back resolves your problem.

When you add it back, iTunes should see it as the same playlist when syncing.

I don't know the cause. Is it possible that you updated the playlist on the device at some point in the past? That may be when iTunes started seeing the playlist (on the device) as a different playlist.

Or it may be a "glitch" caused by minor data corruption on the device, that makes iTunes see it as a playlist you updated on the device (even if you did not).

If iCloud Music Library was turned ON, and you turned it OFF, perhaps that is somehow related.

Did removing that playlist in sync setting for Music, confirming it's gone on device, and then adding it back, resolve the issue?

Do you sync an Apple device (like an iPod or iPhone) directly with your iTunes library, that has the same playlist?