Scroll Rect Snapping

I followed this tutorial (https://www.youtube.com/watch?v=jWbAaBEQpvE#t=515.060786) and have gone through it several times from start to finish, but cannot get my scroll rect to snap. The scroll rect goes on forever (I have it set set to unrestricted according to the tutorial). What could I be doing wrong?

Here's a video of my issue in action and a look at my hierarchy - https://youtu.be/YGUOsvauQhc

Here's my code as well:

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class ScrollRectSnap : MonoBehaviour {
 
     public RectTransform panel;
     public Button [] bttn;
     public RectTransform center;
 
     private float[] distance;
     private bool dragging = false;
     private int bttnDistance;
     private int minButtonNum;
 
     void Start(){
 
         int bttnLength = bttn.Length;
         distance = new float[bttnLength];
 
         bttnDistance=(int)Mathf.Abs(bttn[1].GetComponent<RectTransform>().anchoredPosition.x - bttn[0].GetComponent<RectTransform>().anchoredPosition.x);
 
     }
 
     void Update(){
 
         for (int i = 0; i < bttn.Length; i++) {
 
             distance [i] = Mathf.Abs (center.transform.position.x - bttn  [i].transform.position.x);
 
         }
 
         float minDistance = Mathf.Min (distance);
 
         for (int a = 0; a < bttn.Length; a++) {
 
             if (minDistance == distance [a]) {
 
                 minButtonNum = a;
 
             }
 
         }
 
         if (!dragging) {
 
             LerpToBttn (minButtonNum * -bttnDistance);
 
         }
     }
 
     void LerpToBttn(int position){
 
         float newX = Mathf.Lerp (panel.anchoredPosition.x, position, Time.deltaTime * 5f);
         Vector2 newPosition = new Vector2 (newX, panel.anchoredPosition.y);
         panel.anchoredPosition = newPosition;
 
     }
 
     public void StartDrag(){
 
         dragging = true;
 
     }
 
     public void EndDrag(){
 
         dragging = false;
 
     }
 }