Comentário oficial
Since it takes time to reflect the edit you made on rekordbox to xml file where iTunes library data is stored.
Even though you edit or add tracks to the playlists of iTunes, iTunes application does not update the xml file immediately.
It take several minutes to update at the latest. This is why the phenomenon in the screenshot occurs.
When playlists in iTunes are edited, please wait for a while or close iTunes and press reload button on rekordbox.
When iTunes is closed, xml file is updated.
If you have further questions, please let us know.
Thanks,
CRM, Pioneer DJ