not shure this correct ,,from experience ,,i use the U-Mix Control Pro and also a akai mpd18 ,,accuried a irig pad ,, the akai and i rig is used for sample control ,, by having all controllers connected and on line the duplicate control for the sample pads do not conflict and can either use the U-Mix to play samples or the akai or i rigs also ,, so my thoughts would be to connect the controllers and see if this is the solution ,, since you are trying to use MIDI control the audio interface should remain the same ,,
i dont think can hurt to try
you might need to regerster the software licence key in your profile in the fourm ,, only can help