If you have the same song on the player twice, but with two different FIDs, it's a duplicate and you can delete one of them. Somehow, you accidentally uploaded the song to the player twice.

The only trouble will be finding which playlists the songs live in so that you don't lose one or the other without realizing it.

And by the way, just because a song has the same title doesn't mean it's a duplicate. I've got five totally different songs on my player titled "Mother". You think some of these artists have got, um... issues?