I am trying to give "skrillex - rock 'n' roll" and "skrillex - scary monsters and nice sprites," which have been put in the same album, the same cover art. However, only the one I downloaded first is getting the cover art, the other one does not accept it. Even when I select both of them to give the cover art, after I click save tag it undoes everything what I did. Here are some screenshots.
Could you please describe how you do the adding of the coverart exactly? There are different ways to do this.
I notice that your track "Rock 'n' Roll" already has 3 covers embedded, inspite in the tagpanel no coverart is shown. Have you scrolled to 2/3 and 3/3 in the cover art display in the tag panel using the arrows shown below this display?