Hello @Paul_Jessop,
Thanks for posting your message here, I’d be happy to take a look at what could be happening here.
First of all, I just want to confirm if the mentioned MP3’s have any special characters in them, special characters in file names are known to cause issues. After verifying that there are no special characters in the file names, I would check the Setting -> Library -> Skipped Files tab to see if they are recognized but failed to import for some reason. Can you confirm that the \DiskStation\music folder is listed as a watched folder under Settings -> Storage? You can also trigger a “Force Rescan” of that folder in the same menu (Settings -> Storage) by clicking the 3-dot menu and selecting “Force Rescan”.
Please let me know if any of those steps resolve the issue but if not, I will need more detailed information on how your system is set up and how your networking environment looks like, you can use this thead as a guide.
Thanks,
Noris