I realize this thread is pretty old, but has anyone found a solution to this problem?
Everyone I know with a KG-1000G has the same audio rollercoaster problem. It starts out loud, ramps down, then back up within seconds. It's really irritating and there seems to be no way to fix it in the settings (nor with multiple returns under warranty).
For a radio priced like a Yaesu, this thing has been disappointing. Also, the fan sounds like a Vitamix full of ice.
I could get past its other issues if my audio didn't have this ramp up, down, up problem.