Rekordbox export problem

I have a problem in my MacBook Air, when I try to export songs to my usb appears a bubble that says Error exporting new files to USB: "One or more files have not been exported, check the log file in the Documents folder."

I read in the Rekordbox support community and they say this is an issue due to Apple's 11.5 update which changed the file permissions.

How can I solve this problem, I need to export new files urgently :). 