Try decreasing the "Gimbal Pitch Smoothness" setting in DJI GO. If it's maxed out, the gimbal will creep for a longer period of time before coming to a complete stop. You don't want to max out the "Gimbal Pitch EXP" setting either since that will make the gimbal tilt very quickly.
If those adjustments do not help, then try calibrating your remote controller in DJI GO. Make sure you move the gimbal wheel to the full up and down positions during the calibration process.