UNSUNG does not require any other mod, so nothing to do with any dependency or what we would of assumed to be a conflict issue. Sometimes steam does not download all the files 100% correctly for whatever reason. I suggest visiting a site like armanam.eu for the torrent or armaholic or other available download places or even just redownload the steam version to save time. If the problem no longer persists then issue solved. If it does persist I'll add it to our feedback tracker on phabricator. Cheers.