Rekordbox Misses Tracks Out When Exporting Playlist To USB

Hello, 

I've been trying to figure out what the issue is but I can't. I have created a playlist that I want to export to my USB so I went through Sync Manager and exported the playlist. However, most of the tracks exported over fine but there a couple that can't be found and hasn't exported to the USB.

The tracks will still play if I play them in iTunes via Rekordbox, but not via the 'Devices' section on Rekordbox. 

I've tried to 'Relocate' through the 'Track' tab at the top, and it comes up with the message 'This file is already in the collection'. 

I've also tried putting the track in the contents folder of my USB and relocating through that pathway but it gives me the same message. 

Any help would be great, thank you.