Standard Asset joystick has issues when using custom resolution

Hi, I am trying to use standard assets Joystick , but when I reduce the resolution to increase the performance (Mobile platform) the stick(hat) doesn't go to the place that it was at first, when I start the scene, Everything is good, but as soon as I touch the stick (Using custom resolution) , the stick will go into a wrong position, there is some screen shots that will help you to understand the problem:

This is the Joystick script in the Standard assets (Unity 5.4.0f3):

 using System;
 using UnityEngine;
 using UnityEngine.EventSystems;
 
 namespace UnityStandardAssets.CrossPlatformInput
 {
     public class Joystick : MonoBehaviour, IPointerDownHandler, IPointerUpHandler, IDragHandler
     {
         public enum AxisOption
         {
             // Options for which axes to use
             Both, // Use both
             OnlyHorizontal, // Only horizontal
             OnlyVertical // Only vertical
         }
 
         public int MovementRange = 100;
         public AxisOption axesToUse = AxisOption.Both; // The options for the axes that the still will use
         public string horizontalAxisName = "Horizontal"; // The name given to the horizontal axis for the cross platform input
         public string verticalAxisName = "Vertical"; // The name given to the vertical axis for the cross platform input
 
         Vector3 m_StartPos;
         bool m_UseX; // Toggle for using the x axis
         bool m_UseY; // Toggle for using the Y axis
         CrossPlatformInputManager.VirtualAxis m_HorizontalVirtualAxis; // Reference to the joystick in the cross platform input
         CrossPlatformInputManager.VirtualAxis m_VerticalVirtualAxis; // Reference to the joystick in the cross platform input
 
         void OnEnable()
         {
             CreateVirtualAxes();
         }
 
         void Start()
         {
             m_StartPos = transform.position;
         }
 
         void UpdateVirtualAxes(Vector3 value)
         {
             var delta = m_StartPos - value;
             delta.y = -delta.y;
             delta /= MovementRange;
             if (m_UseX)
             {
                 m_HorizontalVirtualAxis.Update(-delta.x);
             }
 
             if (m_UseY)
             {
                 m_VerticalVirtualAxis.Update(delta.y);
             }
         }
 
         void CreateVirtualAxes()
         {
             // set axes to use
             m_UseX = (axesToUse == AxisOption.Both || axesToUse == AxisOption.OnlyHorizontal);
             m_UseY = (axesToUse == AxisOption.Both || axesToUse == AxisOption.OnlyVertical);
 
             // create new axes based on axes to use
             if (m_UseX)
             {
                 m_HorizontalVirtualAxis = new CrossPlatformInputManager.VirtualAxis(horizontalAxisName);
                 CrossPlatformInputManager.RegisterVirtualAxis(m_HorizontalVirtualAxis);
             }
             if (m_UseY)
             {
                 m_VerticalVirtualAxis = new CrossPlatformInputManager.VirtualAxis(verticalAxisName);
                 CrossPlatformInputManager.RegisterVirtualAxis(m_VerticalVirtualAxis);
             }
         }
 
 
         public void OnDrag(PointerEventData data)
         {
             Vector3 newPos = Vector3.zero;
 
             if (m_UseX)
             {
                 int delta = (int)(data.position.x - m_StartPos.x);
                 delta = Mathf.Clamp(delta, - MovementRange, MovementRange);
                 newPos.x = delta;
             }
 
             if (m_UseY)
             {
                 int delta = (int)(data.position.y - m_StartPos.y);
                 delta = Mathf.Clamp(delta, -MovementRange, MovementRange);
                 newPos.y = delta;
             }
             transform.position = new Vector3(m_StartPos.x + newPos.x, m_StartPos.y + newPos.y, m_StartPos.z + newPos.z);
             UpdateVirtualAxes(transform.position);
         }
 
 
         public void OnPointerUp(PointerEventData data)
         {
             transform.position = m_StartPos;
             UpdateVirtualAxes(m_StartPos);
         }
 
 
         public void OnPointerDown(PointerEventData data) { }
 
         void OnDisable()
         {
             // remove the joysticks from the cross platform input
             if (m_UseX)
             {
                 m_HorizontalVirtualAxis.Remove();
             }
             if (m_UseY)
             {
                 m_VerticalVirtualAxis.Remove();
             }
         }
     }
 }