musicstation Permission denied for playlist

[actlhm]

Hello,

yesterday I created a playlist within musicstation and could play the songs. Today when I click the playlist and select "Play" it loads the playlist into the player-bar but then I get a "System Information: Permission denied" error. All songs in the player have a red sign behind the title.
I'm always using the same user, I've not added or removed any song on my disk since yesterday. I shutdown the qnap (ts-210) overnight.
Has anyone an idea what the problem is? Do I have to create a new playlist every day?

thanks