2D Background Scrolling Problem - Twitching

I need 2D SCROLLING BACKGROUND.
In Unity Editor - Background twitches. On ios device - twitching increases. And after 10 minutes background move more jerkily.
I play with VSyncCount - does not help.
Get Demo project .

 using UnityEngine;
 using System.Collections;
 
 public class BackgroundScroller : MonoBehaviour {
 
     public float speed = 0.05f;
     public bool isRunning = true;
 
     private Vector2 offset;
     private Renderer rend;
     
     private float timeCounter = 0f;
 
     void Awake()
     {
         rend = GetComponent<Renderer>();
     }
 
     void Update () 
     {
         if (isRunning) 
         {    
             timeCounter += Time.deltaTime;
             offset = new Vector2(timeCounter * speed, 0f);
             rend.material.mainTextureOffset = offset;
         }
     }
 }

What's wrong?

P.S. If i use offset scroller - the same problem