The copter flies and I hear no howl. A backwards spinning prop should howl and a reversed motor should flip.
I am more inclined to think offset board (the front of the board not facing the front of the copter) or a reversed yaw channel. As the copter tries to steady itself it applies a touch of yaw to counter the spin detected by the gyros, but the channel is reversed so the copter is countering a right yaw with MORE right yaw instead of left yaw. What you would see is a copter that spins slowly to start but picks up spin speed while maintaining a level hover.
Check out step 6 in the link and see if yaw is reversed. Be sure the front of the KK2 points toward the front of the copter.
Pop the copter up. Don't slowly ramp up and slowly lift off a copter. Dirty air under the props will cause the copter to oscillate. I don't lift off from concrete any more. I put a dinner plate out in the middle of soft, cushy grass and launch from the plate. This way when I pop it up, if it's jacked, I can chop throttle and ditch it in the grass without breaking a boom or a bell.