Need help debugging: SiblingIndex

Hi there!

Trying to create a card game. Player should be able to rearrange the cards in their hand. To show where the card the player is currently dragging was before I create a placeholder. The placeholder is destroyed at the end of the drag. Everything runs pretty smooth, but when I rearrange the cards for a while it gets a little chaotic: at the end I always have 1 card that is at a different SiblingIndex as it should be. Would be lovely if you could take a look please.

Here's the code: (every GameObject Card got a Script(c#) called Draggable)

 using UnityEngine;
 using System.Collections;
 using UnityEngine.EventSystems;
 using UnityEngine.UI;
 
 public class Draggable : MonoBehaviour, IBeginDragHandler, IDragHandler, IEndDragHandler
 {
     
     public Transform parentToReturnTo = null;                    
     public Transform placeholderParent = null;
     public GameObject placeholder = null;
 
     //public GameObject preFab;
 
     
     public void OnBeginDrag (PointerEventData eventData)
     {
         
         placeholder = new GameObject ();
         //placeholder = Instantiate (preFab) as GameObject;
         parentToReturnTo = this.transform.parent;                        
         placeholder.transform.SetParent (parentToReturnTo);
         placeholder.transform.SetSiblingIndex (this.transform.GetSiblingIndex ());    
         placeholder.transform.localPosition = this.transform.localPosition;
         placeholder.transform.localRotation = this.transform.localRotation;
 
         this.transform.SetParent (this.transform.parent.parent);
         this.GetComponent<CanvasGroup> ().blocksRaycasts = false;
 
     }
     
     
     
     
     
     public void OnDrag (PointerEventData eventData)
     {
         this.transform.position = eventData.position;
         
         placeholderParent = placeholder.transform.parent;
         int tempSI = placeholderParent.childCount-1;
         for (int i=0; i < placeholderParent.childCount; i++) {
             if (this.transform.position.x < placeholderParent.GetChild (i).position.x) {
                 tempSI = i;
                 if (placeholder.transform.GetSiblingIndex () < tempSI)
                     tempSI--;
                 break;
             }
         }
 
         Vector3 tempPos = placeholderParent.GetChild (tempSI).transform.localPosition;
         Vector3 tempPosPlace = placeholder.transform.localPosition;
         Quaternion tempRot = placeholderParent.GetChild (tempSI).transform.localRotation;
         Quaternion tempRotPlace = placeholder.transform.localRotation;
 
         placeholderParent.GetChild (tempSI).transform.localPosition = tempPosPlace;
         placeholderParent.GetChild (tempSI).transform.localRotation = tempRotPlace;
         
         placeholder.transform.localPosition = tempPos;
         placeholder.transform.localRotation = tempRot;
 
         this.transform.localRotation = tempRot;
 
         placeholder.transform.SetSiblingIndex (tempSI);
     }
     
     
     
     
     
     public void OnEndDrag (PointerEventData eventData)
     {
         this.transform.SetParent (parentToReturnTo);
         this.transform.SetSiblingIndex (placeholder.transform.GetSiblingIndex ());
         Vector3 temp = placeholder.transform.localPosition;
         GetComponent<CanvasGroup> ().blocksRaycasts = true;
         Destroy (placeholder);
         this.transform.localPosition = temp;
     }
     
 }