Unity - Why iPhone 6 and 7 behaves differently to touch input?

Question

I have below code in Update() to drag camera and also detect clicks on objects. When we try on iphone 6 and X it works all well, but when we try on iPhone7 the drag screen is very unresponsive and clicking objects works only when you touch the screen very very lightly. Anybody have an idea on what is going on?

if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Began) {
             fingerMoved = false;

             if (_eventSystem.IsPointerOverGameObject(Input.GetTouch(0).fingerId)) {
                 fingerMoved = true;
             }
             hit_position = Input.GetTouch(0).position;
             camera_position = cam.position;
         } else if (Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Moved) {
             current_position = Input.GetTouch(0).position;
             LeftMouseDrag();

             if (Vector2.Distance(hit_position, current_position) > 7f) {
                 fingerMoved = true;
             }

             cam.DOMoveY(target_position.y, 0.75f);
         } else if (!fingerMoved && Input.touchCount > 0 && Input.GetTouch(0).phase == TouchPhase.Ended) {
             foreach (var item in storageList) {
                 if (Vector2.Distance(item.transform.position, Camera.main.ScreenToWorldPoint(hit_position)) < 0.5f) {
                     sideMenu.Open(item.myNo);
                 }
             }
         }
 void LeftMouseDrag() {
     Vector3 direction = Camera.main.ScreenToWorldPoint(current_position) - Camera.main.ScreenToWorldPoint(hit_position);
     direction.x = 0f;
     direction = direction * -1;
     target_position = camera_position + direction;
     if (target_position.y > camMaxY) {
         target_position.y = camMaxY;
     }
     if (target_position.y < camMinY) {
         target_position.y = camMinY;
     }
 }

Answer 1

The problem has gone by itself, I have no idea what went wrong at first.