iPod Artist names doubled up when using select sync in iTunes

[luckylisp]

I don't sync my entire library to a couple of my iPods so I use the only sync selected artists/playlists etc. The weird problem is under where artists are listed many times the artist's name will appear twice.

Any idea why this would be happening and what I can do so they appear only once?

 

[LaWally]

Has this always been the case or is this a new problem? How many is "many"? Screenshot?

 

[luckylisp]

It's been the case for awhile now. I'd say maybe 50 artists. Here's an example.
You'll note 4 artists in this screen shot.

I'm assuming it must be the tagging, but when I look at them I can't see what would be causing it. That said, if I keep redoing them, as in change the album title, or artist, and then change it back, it will only list once then eventually. Some I've had no luck with though and sometimes I really have to mess around with it to get it to change. Do I literally have to do this for every artist that is doubled up to fix it?