I have been running Mac OS X Mojave for a while now, and I am super happy about the new dark design. For once Rekordbox worked fine in the transition between High Sierra and Mojave (version 5.4.0), but when the officiallly Mojave compatible Rekorbox was released, the 5.4.1, they managed to screw things up. On this version, and when exporting my rekordbox to my external disk/stick then all of a sudden I get duplicates. FYI, I have my original files on an external drive and my Rekordbox dB on that same drive. So when I export my “rekordbox” to my drive, I don’t need duplicates.
So, the solution was to revert back to an older verson Rekordbox, and I will keep the 5.4.0 version until they have fixed the issue. I have seen in the Forum that other people have similar problems, so I am sure PioneerDJ is working on a solution.
If you have had problems with Rekordbox 5.4.1 as I have, and want to revert back to an older version Rekordbox yourself, use the following link and download whatever version suits you the best: https://forums.pioneerdj.com/hc/en-us/community/posts/115017868983-rekordbox-Download-Archive
Don’t worry keep happy!