So, delete you iTunes Library, setup it up again and all you issues will gone.
Also delete the iTunes folder from music folder on synology, it’s just metadata that u don’t need anymore as u will have a new scan anyways, and let this new iTunes folder created on the BlueIris PC.
A much cleaner setup and hassle free as you don’t need to refresh iTunes Library, just reconnect to Synology iTunes Server and all new music will appear in seconds. One last thing, if you have a huge library it will take sometime and u might have the iTunes app hangs, just leave it and see next day if it finishes or u might need to kill it and reconnect again!