cleaning up inconsistencies in file name encodings.
Reminder: it's a double url escaped encoding, with '/' specifically encoded
  as '%2F' (or %252F after the double encoding).  This is done for ease of
  use when loading the files.  Confusing for generation but much easier
  at the end point when mhen making requests as we don't need to remember
  to escape it, it can just be given without alteration.