So if I had a cp -v operation fail, is the last file name it printed out the last successful file copy, or is it the failed partially copied file? If you had to ensure all files are copied correctly without overwriting anything, would deleting the last filename that was printed from the destination folder delete the partially copied file that the operation failed on?
Run an md5sum command on the last file in each location and compare. That will tell you if one of them is different and answer your question.