I found a way to fix this error. What i did was open command prompt as an administrator and wrote "format x: /q" replace x by the letter of your drive. cmd will ask you to force dismount - approve. It said i got something invalid after but
right after i did that, i went in wbfs manager and format worked!!
you can also try compuapps swissknife and format it to fat32.
its not guarantied to work but it did for me.