So I've found a bug when working with audiobooks.
Folder1: ItemA - ItemB
Folder2: ItemA - ItemB - ItemC
When using Format Value "_DIRECTORY" to modify the directory from:
ItemA - ItemB\File1.mp3
...then any file in Folder2 is affected. The program seems to think that anything anything in Folder2 has now been changed. The program now thinks that Folder2 is:
RenamedA - ItemC\FileX.mp3, although no modifications to files in this directory, or the directory itself. Since that's the case, the files are now inaccessible because the program is looking in the wrong place. It shouldn't be modifying Folder2 either way.
Also, just to verify, I checked with Folder3 & Folder4 and changing Folder3 from AABB to Renamed2 makes the program think Folder4 is now Renamed2CC even though no files or folders should have change.
I tried this with 'Tag to Filename' and there's no problems.
The problem only occurs when using the 'Format Value' option in Actions.
Personally I'm using: Format Value "_DIRECTORY" and %artist% - %album% - %title% or similar, but with some playing around I found any use of the Format Value action does this, that's how I discovered that no spaces are required.
I hope I've made the bug clear enough. It's a little annoying, but I haven't run into it a huge amount. If you need a better explanation please post and I'll try and explain further.