I tested this on my PER and at first I didn't think what you described was happening. I was listening for a higher pitched audible click of some sort. But then after a few more times I picked up on it. I thought I was hearing the sound of my microKontrol mini keys hitting the the bottom of the board, but it disappeared after cycling through the voices and realized that was what you were describing.  It is there, but if you hadn't mentioned it, I likely never would have realized it. Blended into a mix I doubt you would hear it at all. It's not terrible, but in a critical listen, you can hear it once you find it.