Clamp Camera Angle not Working

Hi there, I am trying to clamp my camera angle and have looked at various topics here but can't work out why it jitters while rotating on specific angles. I have some ideas, but even so I'm not sure how to fix it.

For example - If my camera is directly behind my character and I raise it up over his head, it clamps perfectly, same with under the character, but if it's been rotated horizontally around the character the camera jitters horribly when I try to move it vertically.

This is the code I'm using:

 void FreeCamera(float mh, float mv)
 {
     float rotationAmount;
     float rotationHAmount;

     if(((mh > deadZone || mh < -deadZone)) || (mh > deadZone || mh < -deadZone))
     {
         rotationHAmount = mh * hRotateSpeed * Time.deltaTime;
         camera.transform.RotateAround(target.transform.position, Vector3.up, rotationHAmount);
     }
     if(((mv > deadZone || mv < -deadZone)) || (mv > deadZone || mv < -deadZone))
     {
         rotationAmount = mv * -1.0f * vRotateSpeed * Time.deltaTime;
         Vector3 currentVector = transform.position - target.transform.position;
         float angleBetween = Vector3.Angle(initialVector, currentVector) * (Vector3.Cross(initialVector, currentVector).x > 0 ? 1 : -1);
         float newAngle = Mathf.Clamp(angleBetween + rotationAmount, -maxAngle, maxAngle);
         rotationAmount = newAngle - angleBetween;

         camera.transform.RotateAround(target.transform.position, cam.transform.right, rotationAmount);
     }
 }