Downloaded Playlists Disapear

[user-removed]

Have had a premium account for a little over two years. Currently running on an iPhone 7 with IOS 11.2.6 (latest release). I can download playlists and play them offline, but about every two weeks they disapear. Checking the library all the playlists have the Dowload switch set to OFF. I can re-download them but in two or three weeks they all dispear again and all download switches return to OFF. This is getting to be a real hassle. I see this as a constant thread on the Android pages as well, so I am pretty sure this is a Spotify problem, not an IOS problem