3 files that continue to fail

[random8675309]

I have what appears to be an odd issue that I can't find any insights on. I have 3 files that fail every time I try to make a m4b from them. I have hundreds that have run successfully but these three always fail. The logs I get are not helpful:

dirname: missing operand
Try 'dirname -- help' for more information
mv: missing file operand
Try 'mv -- help' for more information

I assumed it was a file ownership issue or permissions issue but I think I have confirmed it is not. I changed the ownership of the files and did a 777 to the directory.

I am thinking it's a file naming issue but I can't see any issues with naming conventions

Folder name: Terry Pratchett - Dark Side of the Sun (1976)
File name format: Terry Pratchett - Dark Side of the Sun -1-5.mp3 (2-5,3-5, etc)

If I add 10 more books to the recently added directory they all process, just these fail.

I am going to try renaming all files in one of these folders to see if it makes a difference. Any thoughts or help are appreciated.