Are you playing them in rekordbox from the export drive, or are you playing them on a CDJ / XDJ?
USB Track Load Errors
I recently updated to version 6.6.1, upon trying to play some of my tracks many of them have a load error. These same tracks play fine in the main collection but off my usb they won't load.
I have tried to auto relocate the "missing songs" but it says all tracks are accounted for. Maybe it was an issue with syncing my library. I have always had this issue with rekordbox previously. Frustrating as I want to play the tracks off my usb for gigs but many are missing. What should I do ?!