Line Renderer - not Perspective?

Hello, i want to set up an easy trail behind a ball (so that it looks that you "paint" while moving the ball). at the moment it looks like this:

the problem is, that the line is getting thiner and thicker depending on the direction. and i want to have i constant - thick line. here are my settings:

the trail renderer is on a different game object then the ball so that the line renderer is not drawn in the middle of the ball. for this i use this script:

 using UnityEngine;
 using System.Collections;
 
 public class CopyPosition : MonoBehaviour
 {
     public Transform itsTarget;
     void Update ()
     {
         transform.position = new Vector3(itsTarget.position.x,0.96f,itsTarget.position.z);
     }
 }

that leads to that the line follows the ball on the x and z axis, but always stays at the Y axis. which is good, no errors here, just want to mention it ;)

so, how can i have a constant thick line with my trail renderer?