I have been using my 9958 for 10+ runs over the past 2 days. There has been a couple of crashes so far. After changing batteries, when I added power, the tail rotor went crazy. Whenever I add the slightest of throttle, the tail rotor spins at near full speed. I need opposite rudder to even make it stop. It spins clockwise when viewed from the top.

Now the heli is un-flyable as it spins crazily on the floor with any power added. Is there a problem with the circuit board? The motor responds to yaw input (full to one side causes it to stop). This means the motor and wiring is intact. The signals for tail motor power is wrong.

How can I fix this?