If you do a history on one of these files through the Vault web browser and pick Diff from previous, you will get the following "error":
Unfortunately, I don’t believe that this is a real error as the same operation works fine through the Client GUI, but no differences are found. I think the real problem is that there is only 1 version of the file and Vault Web Diff does not handle this case correctly. Instead of proclaiming there is an error (in big, bold red type), it should say that the files are identical.Unable to retrieve diff.
Error=FailObjectVersionLookup