Popping sound when whistling with Play Acoustic


I use Play Acoustic extensively and a huge fan. I have one issue I can't seem to fix, namely I get a popping or crackling sound when I whistle. It is not air noise, I've tested that and I get it when listening to the headphone out on the Play Acoustic itself so it is not somewhere else in the signal chain. It almost sounds like some kind of signal clipping but it happens at all gain settings. This is an amazing unit and perhaps this is simply a type of sound it cannot process. Any suggestions are appreciated. I have tried everything I can think of. BTW, it doesn't seem to be an effect generated problem as it is present in a dry signal.