I had issues with the Phantom leaving a hover when the yaw stick was used.  I almost lost the plane once, engaging the RTH when the Phantom was 400 feet away from where it was hovering previously.  

I almost crashed another time when the Phantom took off on it's own from a hover when the yaw was activated.  

It was pretty scary for a new pilot.  I re-calibrated the sticks several times to no avail.  

I checked the IMU numbers and saw the yaw numbers were off.  An advanced IMU calibration corrected the problem.

I suggest that the IMU calibration be checked before the first flight.

"I suggest that the IMU calibration be checked before the first flight."

Good advice.