MediaBay not saving changes to tags/attributes

Hi all,

I’m trying to organise my MIDI files by tagging them with the category (piano, drums etc.), sub-category and also the Family Name in the MediaBay.

When I changes these fields, I can see the new values in the MediaBay, but as soon as I exit and re-enter the MediaBay, the values haven’t saved.
If I change the “Key” field, it does save.

The files are not write protected. I’ve looked at the column in the MediaBay and also in Windows Explorer.

Is it not possible to change the “Category”, “Sub-Category” and “Family Name” fields in a midi file?
These are SMF type 1 files.

I’m on Cubase Pro 8.5 64 bit on Win 10