If you edit your playlist, some music is removed of download. Also, after a few weeks without going online in Spotify, music loses downloads.
I don't know what the issue is, but reinstall Spotify and download all your music again. (Reinsall so it doesn't take extra space above the 3 GB.
What's even more annoying is people who don't read. Scroll to the very bottom of this or any other community page and you'll see an "About" link which takes you the the page with ways to get in touch with Spotify. Good luck.
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