Spotify undownloads my playlist songs when I go offline

[LuckyTrash]

Hi! I travel constantly, and I carry around my ipod everywhere with me. Since it is an ipod, it constantly goes on and offline. I pay premium and I have my playlists downloaded before I leave, so I can listen to my songs offline. A problem I have been having lately is that my playlists will undownload themselves. It will do it at random times, and the only way is to get my songs back is to connect to wifi and redownload everything. Again.. And again.. Seems to mainly do this to my main playlists I listen to??? What do I do? 

[xodejabear]

The same things happens to me on my iPhone 6. I had downloaded everything so I could listen offline while on vacay in Cuba. I get to Cuba, it's all gone. It's not the first time this has happened either. I'm constantly re-downloading my songs, but never have anything in my library (off-line). Getting super annoyed by this, as I am a long-time paid subscriber. Please help!!