Local files won't sync

[sseebbee95]

I have added files to the folders and added the folders to sync. However they only work for a short period of time. They show up, I can add them to a playlist and sync them to my phone. However next time I start up spotify I need to readd all the files into the selected folder to get them back on spotify (desktop). On my phone they stay and once I have manualy resynced them to spotify they automatically show up again in my playlists.

Anyone have a solution or explanation on why it desyncs? All files are MP3.