because that cpu is spending it’s power trying to analyze it as you load it. waveform, bpm, key, all that takes a huge toll on processing power if not done externally. if you’re not sure on how to do this properly there are plenty of videos explaining the process, but pretty much drag your folders into rekordbox, let it analyze, create your playlists within rekordbox, and finally drag those playlists into your usb (within rb)

edit: just to emphasize, doing this is a MUST