Hello,
I have looked arround and it seems you have no dedicated system for users to submit bug reports to your software team so I am submitting one here.
OS: Windows 7 64bit
Rekordbox version: 5.0.1/5.0.2
Controller: DDJ-RB
When First opening Rekordbox (version 5.0.1) with my DDJ-RB controller plugged in I can not load songs. I can use the scroll knob on the controler to find a song, I can push the "Load" button and the song title will appear on the deck I chose to load it to, but the waveform never shows up and the play button will not play the song. As soon as I unplug my controller the waveform will load, then sometimes I can plug the controller back in and it will work, but very frequently It will not. After that its a random process of restarting rekordbox multiple times, plugging in and unplugging my controler until it decides to work.