have you checked the permissions on these FLAC files? Do that and make sure you have all the proper security rights. Are you using XLD for these FLAC rips? XLD does something strange with the file metadata and I have had issues with FLAC files on another device as I also use XLD. If that is the case, try and re-rip a disc using another FLAC program and test this. There are some cmd line moves I believe that you can use to fix the metadata on your other files if that is the issue.