I have added/modified and succesully managed the tags for almost all music files I ripped from my CD collection.

In a few very select cases I seem to be unable to modify a specific tag.

Example:
In the navigation pane on the left an album is listed as "AC / DC (Back in Black)"
I have checked and tried to edit the parenthesis values, but there appears to be no area where that is stored. Neither on the left nor the advanced tag area. Whenever I click EDIT, only the AC / DC part shows.

What am I missing?