Please help, Unity bugs or not?

I trying to make infinite runner. Ive made a plane which 2x2 and a script which fill place. It works like fill place 3x25 and start move -x coordinate. if some child has x: -2 coord it will destoy, if childcount < 3*25 it instantiate a 3 new. But here somehow little holes

Ive change logic of script, now childs doesnt destroying they just change them position to some coords and move back when childcount < 3*25 but it still buging

I cant find where my mistake do. Havent attach for the code so here is. P.s. increase gamespeed increase holes like that.

 using UnityEngine;
 using System.Collections;
 
 public class LevelScript : MonoBehaviour {
 
     public float widht_field;
     public int game_field_lenght;
     private float NextPosX;
     public float gamespeed;
     private GameObject LevelEmpty;
     private GameObject TmpObj;
     private float ZCoord;
     private GameObject CollectedFields;
 
     // Use this for initialization
     void Start () {
         ZCoord = -widht_field;
         LevelEmpty = GameObject.Find("LevelEmpty");
         GameObject Fields = new GameObject("Fields");
         CollectedFields = GameObject.Find("Fields");
 
         SpawnObjects();
 
         FillScene();
         NextPosX -= widht_field;
    
     }
     
     // Update is called once per frame
     void Update () {
     
     }
     void FixedUpdate()
     {
         Debug.Log(Time.deltaTime);
         LevelEmpty.transform.position = new Vector3(LevelEmpty.transform.position.x-(gamespeed*Time.deltaTime),0,0);
         CollectedFields.transform.position = new Vector3(200,0,0);
         int count = LevelEmpty.transform.childCount - 1;
         for (int i = 0; i < count; i++)
         {
             if (LevelEmpty.transform.GetChild(i).transform.position.x < -2)
             {
                 LevelEmpty.transform.GetChild(i).transform.position = CollectedFields.transform.position;
                 LevelEmpty.transform.GetChild(i).transform.parent = CollectedFields.transform;
                 i--;
                 count--;
 
 
             }
         }
         //foreach (Transform field in LevelEmpty.transform)
         //{
         //    if (field.position.x<-2.0F)
         //    {
         //        field.gameObject.transform.position = CollectedFields.transform.position;
         //        field.gameObject.transform.parent = CollectedFields.transform;
 
         //    }
         //}
 
         for (int i = 0; i < 3; i++)
         {
             if (LevelEmpty.transform.GetChild(i).transform.position.x < -2.0F)
             {
                 LevelEmpty.transform.GetChild(i).transform.position = CollectedFields.transform.position;
                 LevelEmpty.transform.GetChild(i).transform.parent = CollectedFields.transform;
 
             }
         }
         if (LevelEmpty.transform.childCount < (game_field_lenght) * 3)
         {
             SpawnField();
         }
     }
     void FillScene()
     {
         for (int i = 0; i <= (game_field_lenght)-1; i++)
         {
             SpawnField();
             NextPosX+=widht_field;
         }
 
     }
     void SpawnField()
     {
         for (int i = 0; i < 3; i++)
         {
             TmpObj = CollectedFields.transform.GetChild(0).gameObject;
             TmpObj.transform.parent = LevelEmpty.transform;
             TmpObj.transform.position = new Vector3(NextPosX, 0, ZCoord);
             ZCoord += widht_field;
         }
         ZCoord = -widht_field;
     }
     void SpawnObjects()
     {
         for (int i = 0; i < (game_field_lenght)*3; i++)
         {
             GameObject tmp1 = Instantiate(Resources.Load("tank_field"), new Vector3(NextPosX, 0, 0), Quaternion.Euler(270, 0, 0)) as GameObject;
             tmp1.transform.parent = CollectedFields.transform;
             tmp1.transform.position = Vector3.zero;
         }
         CollectedFields.transform.position = new Vector3(-200,0,0);
     }
 }