CustomScroll inherited from RectScroll, executing in edit mode

Hello, I faced weird issue, that I can't understood.

I made CustomScroll class inherited from RectScroll. Everything was okey to the moment, when my public variables disappeared from Inspector. In my Custom class I made two things, Instantiating Items at Start() and made LateUpdate() for Lerping content position to center on closest item.

For some reason after I exiting PlayMode in Editor, I can see items that was instantiated in PlayMode, they are not removed after. If I will run game few times, I will have list with a lot of duplicates.

After Debuging Start() function, I can see, that it executes two times, one in PlayMode, and after exit PlayMode in Editor. Using new Unity2017.01.

Why is this happening, Is this issue ?

Edit1: If I understanding right, RectScroll have [ExecuteInEditMode] and functions that CampaignScroller.LateUpdate() hides inherited member UnityEngine.UI.ScrollRect.LateUpdate()z runs in Edit mode. Can I turned it off ?

Console: Debug.Log (Application.isPlaying);

Code:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class CampaignScroller : ScrollRect {
     int currentMapIndex = 0;
 
     public Text currentName;
 
     public GameObject itemPref;
 
     void Start(){
             Debug.Log (Application.isPlaying);
         Initialize ();
     }
 
     void Initialize(){
         foreach (CampaignManager.Mission mis in CampaignManager.missions) {
             GameObject go = Instantiate (itemPref, content) as GameObject;
             if ( mis.IsDone () ) {
                 go.GetComponent<CampaignItem>().SetAsActive ();
                 go.GetComponent<CampaignItem>().SetStars (5);
             } else {
                 go.GetComponent<CampaignItem>().SetAsDisabled ();
                 go.GetComponent<CampaignItem>().SetStars (0);
 
             }
         }
     }