Audio feedback probelm solved after hours of setting changes, software changes (2.20 vs 2.27), changes to my MicroHam router interface.
The solution(?) was simple. While playing with HRD adjusting my rigs microphone gain, I noticed on my Pro III band scope (via remote camera), that the problem when away with zero mic gain, came back with any significant gain. I set the AF volume to zero, same thing. Next adjusted thae AF gain back to mid range, problem 'disappeared'.
The crazy thing is.. I had rebooted the system a number of times (changing software versions & settings) and power cycled both RRC devices and the remote radio many times. Adjusting the rig AF several times, including zero.
Maybe the problem will 'reappear' in the future, but today the system is behaving properly.
Ken-W9KB