Engine Prime Crashing when syncing USB

Engine prime constantly crashes when syncing to USB. It gets to the final part hen crashes every single time. My USB is new, it was working last week. This happens with Engine Prime 1.5 & 1.5.1. Ive scanned and repaired any corrupted music files, replaced and dropped back into EP. Same issue constantly happens. Really annoying. No issues on a maintenace to the USB via disk utillity. Using a MacBook Pro OSX Mojave 10.14.6 Any constructive advice appreciated.