I have all my MP3 files stored on a QNap NAS box, whenever I try to modify and save the ID3 tag using mp3tag, I get an error which says (filename) cannot be opened for writing.
The only way I can update the ID3 tag is to copy the files to my desktop, edit the tags and then save them back to the NAS.
Insufficient access rights,
other program on NAS (or whereever) tries to access the files simultaneously
something like this.
I would not use the data on the NAS for extensive editing anyway as the network speed is by the power ten slower than access to the local hard disk. So I would copy the files, do the editing, copy them back again.