Does anyone know why those blue lines appear when the camera and background moves?

When the player, the camera and the background start to move, several blue lines appear in front of the platform that I suppose are from the background. The camera has a script to follow the character and the background is children of the camera.

This is the camera script:
// Smooth towards the target

     using UnityEngine;
     using System.Collections;
     public class DampCamera2D : MonoBehaviour
         public Transform target;
         public float smoothTime = 0.3F;
         private Vector3 velocity =;
         void Update()
             // Define a target position above and behind the target transform
             Vector3 targetPosition = target.TransformPoint(new Vector3(0, 1, -10));
             // Smoothly move the camera towards that target position
             transform.position = Vector3.SmoothDamp(transform.position, targetPosition, ref velocity, smoothTime);

Here is an image, there is only one line but when I move the character a lot more appear:

I hope yo can help me! Thanks in advance.

I figure it out how to fix this problem thanks to this Youtube 1. The problem was solve by creating an Sprite Atlas and adding to it all the tilesets I was using, then in the sprite atlas configuration i set Compression to None and Filter Mode to Point. I hope my research help other people!