Can't export to USB – even after wiping laptop entirely

Hey all, 
I'm running a late 2013 Macbook Pro 15" with Rekordbox 5.3. 
I've never had any problems before but since I downloaded latest version I can't export anything. This has already ruined two DJ shows for me. 

To be safe i did a clean install on OSX, my entire music collection & Rekordbox.
I thought this would solve it, but after nearly 2 days of redownloading my collection (on my hard drive but also synced with Google Drive) i am getting the exact same result. 

I go to export & it stays on 0% & freezes so I have to force quit. 

Any help here would be amazing. 

Thanks