I have this similar issue with the XDJ-RX2. If I upload 200 songs to 1 playlist to an external USB Thumb Drive. Performance is just fine. But, if i upload 1000 songs to 1 playlist. The thing starts going bonkers after 1 or 2 hours of playtime. Song load times and GUI load times become astronomical and the unit appears to be freezing. The issue is not isolated to a single brand of thumb drive as i use patriot, samsung and sandisk with the same result. All at 128GB of storage formatted in FAT32. I operate the unit in standalone mode.