Yaw setpoint failure due to Magnetic Field

I´m building a Standard VTOL with the Fun Cub Quad VTOL airframe. The aircraft behaves ok in pitch and roll but keeps trying to make a yaw clockwise maneuver when its in the air even when the yaw setpoint should be zero. My external GPS/Compass is on top of the vehicle away from other electronic devices. I´ve twisted the current cables that go from the distribution circuit to the motors and I´ve placed them as far as posible from my pixhawk. The thing is that I keep having interference and noise when I turn the motors on. Any suggestions??

The Log file is this