I'm randomly having this error pop up on some of my client files when I back them up "System.ArgumentException: An item with the same key has already been added."

This happens when I back the file up locally or in my shared drive (so I can access my files on another computer) it's feeling random, I can't figure out a common thread about why some clients have the error, and others don't. Sometimes the file will give me the error but still back up, but then I can't restore the file on my other machine. 

Anyone else getting this issue? After two+ hours on the phone with Lacerte we haven't found a solution.