Spotify downloads all of my songs again

[user-removed]

I have Spotify Premium and both streaming and download quality is set to extreme quality.

For some strange reason the Spotify app on my Samsung phone starts to download all of my songs again. I turned the phone from flight mode back on to normal mode and Spotify started to download all my songs again. None of the streaming/download settings where changed which could have caused this. 

Spotify has done it before on a previous (android) phone.

Any good suggestions to why this happens?