with the motor disconnected, but power to the heli, move the cyclic left and right, i bet you can see the swashplate moving up and down on the shaft which it shouldnt be doing, maybe one of your servo's is screwed , the two rearward servos when you give left cyclic or right cyclic should move opposite of each other and in the same exact amount of travel, if one travels farther than the other it affects the pitch.