Why are my downloaded songs removed from my Apple Music playlist?

Hi,

I have raised this with Apple support a few times but no resolution.

The issue is that songs I have downloaded are being removed.

It's almost like it is shuffling all my music and adding and removing songs.

I thought it might be the Favourites Playlist but can't be sure.

I have tried logging out and removing all downloaded songs and redownloading again. Still issue persists.

Any ideas? It's so frustrating.

Thanks.