In other words, I think you've got two copies of each of these songs on your Empeg. As each pair shares the same title, album, and artist, Jemplode probably downloads both to the same place, overwriting one with the other, and leaving you with an arbitrary one of the two. Meanwhile, following your usual playback menus in the web interface gets you only to the good versions.

It's even possible, I suppose, that it's the very existence of these duplicates that's confusing Jemplode's fetch-using-Hijack code.

Peter