I got all ready to swap keys around, but when I took the top panel off, the key noises disappeared. It appears that on this REV2 (and the first one I had), the keys from F4 to B4 lightly hit the inside top of the panel. In the picture below, you will notice some white markings on the inside of the top panel where the F4, G4, and B4 keys are lightly hitting. Out of curiosity, I rubbed the white spots off and put the panel back on. I then played those same keys again, and then took off the panel again. The white spots reappeared in the same locations. Again, exactly the same thing occurred with the first REV2 I had -- although I'm saying that only because the key noise was the same. Did not take the first REV2's top panel off. Sent this information off to DSI's great support, and look forward to knowing what to do next. Love this REV2, that's for sure!