Can't delete playlist: 'there was a problem deleting the playlist'

Hello,

I've got PMS (1.1.4.2757) running on a Synology DS216Play (latest) and it works mostly fine. However, I can't seem to delete playlists. The playlists are imported via an iTunes XML. Somehow, most playlists are doubled, showing both a newer and older version. I figured I just delete them all and redo the import, hoping everything will work out.

Unfortunately I can't seem to delete playlists. I get the message "there was a problem deleting the playlist". I tried restarting PMS, rebooting the Synology, enabling 'Allow media deletion', 'Optimize database', however, to no avail.

Anyone any thoughts on how to fix this. I'd rather not reinstall PMS as reindexing will take quite some time.

Thanks in advance and kind regards, Maarten