I´m premium user

How do I fix the songs?
And why does my playlist undownload?

I have Downloaded the songs  and Random  songs plays but no sound. I cant fastforward or back in the songs, they just reset to 0.00 and keep playing until its done, After the song is done it dont go to the next song,

First it was ONLY red hot chili peppers albums but not the latest album.
But FOR SOME FRUSTRATING reason SPOTIFY made all my 1200 songs undownloaded. (this happens from time to time and it REALLY PISSES ME OFF) because I need to use up all my internet for that month(s) to get them back downloaded

So I downloaded them all again. BUT now ALOT,like 50% of the songs  play but no sound , and wont continue to play after the song ended it just stop at song end (3.12 etc)

So I manualy need to skip to the next song and that song maybe just plays fine but then the next song after might have the same problem.

If I go online the song plays just fine, but as soon as I go back to offline SAME PROBLEM.
Its not every song JUST RANDOM songs, Some songs work on a album and others dont

And if someone suggest to check my volume I will highfive that person in the face. I´m very angry that I actauly pay for this.

I have a samsung S2. And have spotify premium via telia  (sweden) phone not bound to telia.