My songs have been desynchronized

[Jules15]

The songs I downloaded to my iPhone to listen offline, are desynchronized without notice. There are more than a hundred songs that should resynchronize, and I do not want it to happen again. I have Spotify Premium and my payments are current. What could have happened? Excuse my poor english. Thanks!

[gmn312]

Yea this has happened about once a week to me lately.  With this newest update, the whole thing crashes frequently and all music disappears and is then unavailable for offline listening.