Local Files being deleted / desynchronised on iPhone 4S

[JakeBlunt]

Hello all, 

Been trying to find a specific thread for this for a while but to no avail. I have a Spotify Premium account and use my iPhone as a secondary device, and I use a lot of local files in a lot of playlists I have. However, recently I have found that local files are just removing themselves from my iPhone. When I go into Online Mode, the tracks show up even when Hide Unplayable Tracks has been selected, but always come up with the 'Track Not Synced: If you own the track, you can sync it from your computer." message. I have the files and can play them on my  laptop, but my mobile device keeps losing the files. Is this a problem others have found; and if so, is there a way to deal with this? 
 

Using App Version 0.6.4.2, iPhone 4S Version 6.1.3.

Many thanks in advance.

[user-removed]

I am having the same issue on my iPhones 5S, and the only thing that works is deleting the app, and redownloading EVERY files, which is a pain in the butt for how often it happens. Have you found any solutions?