First plug your controller into the RC software assistant and calibrate your sticks and the X1 as prescribed. Then plug the Phantom into the Phantom software assistant and calibrate the X1 control.
If you are still having pitch issues, go into the gimbal settings and make sure that all the controls lines are set to the middle.
Call 844 312 8444 if you have further questions.
DJI downloads site: http://www.dji.com/product/phantom-2-vision-plus/download
If you are using a PC be sure to also download the DJI WIN DRIVER INSTALLER