Detection of Overlap is offset by about 16.5f and increases based on scale.

Two scripts one for Slot one for Item.

Issue

Once scale of Item goes over 4x4 the Overlap detection goes off by about 16.5f. Ideally the detection be right and on point no matter the scale even at 100x100. I believe core problem is inside Slot Script between lines (58-61).

SetUp

Panel

GridLayoutGroup apply following settings

• CellSize (X = 35, Y = 35)

• StartCorner (Upper Left)

• ChildAlignment (UpperLeft)

  ---

Image

Apply Slot Script bellow and attach as child to Panel

• D_Color = Hex B0B0B0

• O_Color = Hex 2ACACF

• Image Source Image = UISprite

  ---

Button

Attach Item Script same level at panel NOT A CHILD OF PANEL

• My Scale (X = 5, Y = 5) or Larger

• Button Colors = Hex 1C1C1C

• Image Source Image = UISprite

  ---

SCRIPTS

Slot.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.EventSystems;
 
 public class Slot : MonoBehaviour, IDragHandler, IDropHandler
 {
     //[HideInInspector]
     public Rect itemRect;
     [HideInInspector]
     public Rect myRect;
     public RectTransform Item_DragRect
     {
         get
         {
             if(Item_CS.Item_Dragged != null)
             {
                 return Item_CS.Item_Dragged.GetComponent<RectTransform>();
             }
             else
             {
                 return null;
             }
         }
     }
     public RectTransform rectTransform;
     public RectTransform rectParent;
     public Rect DisplayRect;
 
     public Color D_Color;
     public Color O_Color;
     public Color T_Color;
     public Item_CS CurrItem;
 
     // Start is called before the first frame update
     void Start()
     {
         rectTransform = this.GetComponent<RectTransform>();
         if(GetComponentInParent<GridLayoutGroup>() != null)
         {
             rectParent = GetComponentInParent<GridLayoutGroup>().GetComponent<RectTransform>();
         }
         else
         {
             rectParent = null;
         }
         
     }
 
     // Update is called once per frame
     public void FixedUpdate()
     {
         
         if (Item_DragRect != null)
         {
             CurrItem = Item_DragRect.GetComponent<Item_CS>();
 
             Vector3[] sCorners = new Vector3[4];
             rectTransform.GetWorldCorners(sCorners);
             Vector2 MyPos = ((Vector2)sCorners[0] * 1);
 
             Vector3[] iCorners = new Vector3[4];
             Item_DragRect.GetWorldCorners(iCorners);
             Vector2 ItemPos = ((Vector2)iCorners[0]);
 
             if(rectParent != null)
             {
                 Vector3[] pCorners = new Vector3[4];
                 rectParent.GetWorldCorners(pCorners);
                 Vector2 ParentPos = ((Vector2)pCorners[0]);
             }
 
 
             myRect = new Rect(MyPos.x, MyPos.y, rectTransform.rect.width, rectTransform.rect.height);
             itemRect = new Rect(ItemPos.x + (CurrItem.MyScale.x), ItemPos.y + (CurrItem.MyScale.y), Item_DragRect.rect.width, Item_DragRect.rect.height);
 
 
             if (!myRect.Overlaps(itemRect))
             {
                 GetComponent<Image>().color = D_Color;
             }
             else
             {
                 GetComponent<Image>().color = O_Color;
             }
         }
         else
         {
             CurrItem = null;
             GetComponent<Image>().color = D_Color;
         }
     }
     public void OnDrag(PointerEventData eventData)
     {
         
     }
 
     public void OnDrop(PointerEventData eventData)
     {
         
     }
 }
 

Item_CS.cs

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.EventSystems;
 using System.Linq;
 
 public class Item_CS : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler, IPointerEnterHandler, IPointerExitHandler
 {
     public static GameObject Item_Dragged;
     public GameObject CurrID;
     public Vector2 MyScale;
     private Vector3 ItemPos;
     public Rect myRect;
 
     public List<Slot> Slots;
 
 
 
     // Start is called before the first frame update
     void Start()
     {
         
     }
 
     // Update is called once per frame
     void Update()
     {
         RectTransform rectTransform = this.GetComponent<RectTransform>();
         myRect = new Rect(rectTransform.localPosition.x, rectTransform.localPosition.y, rectTransform.rect.width, rectTransform.rect.height);
         rectTransform.sizeDelta = new Vector2(MyScale.x * 35f, MyScale.y * 35f);
         DragFunction();
         CurrID = Item_Dragged;
         if(Slots.Count != MyScale.x * MyScale.y)
         {
             Slots = new Slot[Mathf.RoundToInt(MyScale.x * MyScale.y)].ToList();
         }
     }
     
     public void DragFunction()
     {
         if(Item_Dragged != null)
         {
             Item_Dragged.transform.SetAsLastSibling();
         }
     }
 
     public void OnBeginDrag(PointerEventData eventData)
     {
         if (Item_Dragged == null)
         {
             Item_Dragged = gameObject;
             GetComponent<CanvasGroup>().blocksRaycasts = false;
         }
         else
         {
             Item_Dragged = gameObject;
             GetComponent<CanvasGroup>().blocksRaycasts = false;
         }
     }
 
     public void OnDrag(PointerEventData eventData)
     {
         this.transform.position = Input.mousePosition;       
     }
 
     public void OnEndDrag(PointerEventData eventData)
     {
         Item_Dragged = null;
         GetComponent<CanvasGroup>().blocksRaycasts = true;
     }
 
     public void OnPointerEnter(PointerEventData eventData)
     {
         if (Input.GetKeyDown(KeyCode.Mouse0))
         {
             
         }
     }
 
     public void OnPointerExit(PointerEventData eventData)
     {
         //throw new System.NotImplementedException();
     }
 }