Phonak Paradise, musical instrument problem

I’ve had Phonak CROS P90 for a week now and there is one issue that is bothering me. I play the Irish tin whistle. In the second octave (D6-D7, fundamental frequencies ~1200-2000 Hz), there is this thump noise or something when I change notes, almost like someone taps on the mic. The higher the frequency, the worse the problem. Sustained notes are fine. My audiologist turned off all additional processing and sound recover, but that didn’t make any difference. What is this?