Not had this prob myself but don't forget when you catch hold of the leg of the P4 (be careful not to make a hurried grab at it) you must try not to alter its altitude (at all), hold it steady and pull down the stick on the controller and hold it there. If you try to pull on the P4 (even just a little bit) the internal 'brains' will try to maintain its stable position and accelerate the respective props.