Change the comma following "Playlists" to a semi-colon, and add a comma following "however", so that the sentence states:
"A Packing List may reference any combination of Track Files and Composition Playlists; however, the set of referenced files must contain no duplicates."
Change the comma following "Playlists" to a semi-colon, and add a comma following "however", so that the sentence states: "A Packing List may reference any combination of Track Files and Composition Playlists; however, the set of referenced files must contain no duplicates."