Linerenderer disappears after second linerenderer appears

I want to draw two separate line renderers in a scene. One line renderer starts as soon as the script starts running, the other line renderer starts after a certain trigger. However, as soon as the second line renderer starts, the line of the first line renderer disappears. A sphere that moves over this line continues moving in the place where the line should be.

This is how I make the different line Renderers:

 LineRenderer StartlineRenderer;
 LineRenderer[] CheckLinerender = new LineRenderer[18];

  void Start()
     {
         StartlineRenderer = gameObject.AddComponent<LineRenderer>();
         StartlineRenderer = GetComponent<LineRenderer>();
         StartlineRenderer.material = StartMat;
         StartlineRenderer.SetWidth(w, w);
         for (int i = 0; i < 18; i++)
         {
             CheckLinerender[i] = new GameObject().AddComponent<LineRenderer>();
             CheckLinerender[i] = GetComponent<LineRenderer>();
             CheckLinerender[i].material = CheckMat[i];
             CheckLinerender[i].SetWidth(w, w);
         }
     }

Afterwards, I go to other scripts to draw the line renderers:

             lineballs0.LINEballs0(StartlineRenderer, StartSphere, StartText3d);
             T1CHECK1.t1Check1(CheckLinerender[0],CheckSphere[0], Check1Text3d[0]);

These scripts look as follows:

 public static void t1Check1(LineRenderer t1c1, Transform Sphere, TextMesh text1)
     {
                 float temp = READER.count;
                 n = 10;
                 float sfy = 50f;
                 t1c1.SetVertexCount(filereader.lastNumberInclusive + 1 + 2 );
                 int k = 0;
                 for (int i = 0; i < filereader.lastNumberInclusive ; i++)
                 {
                     Vector3 vtemp;
                     vtemp.x = -200 - 1 * (float)i + filereader.lastNumberInclusive / 2;
                     vtemp.y = sfy + TEST1.Check1[0, i];
                     vtemp.z = 200;
                     t1c1.SetPosition(k, vtemp);
                     k++;
                 }
                 Vector3 vPos;
                 vPos.x = -200 - 1 * (temp - n) + filereader.lastNumberInclusive / 2;
                 vPos.y = sfy + TEST1.Check1[0, temp - n];
                 vPos.z = 200;
                 Sphere.position = vPos;
                 text1.transform.position = vPos;
                 text1.text = TEST1.Check1[0, temp - n].ToString("0");
         }

AND:

 public static void LINEballs0 (LineRenderer lineRenderer, Transform Sphere, TextMesh text1) 
     {
         float sfy = 3f;
         int temp = READER.count;
         if (temp < 0)            
                      temp = 1;
         lineRenderer.SetVertexCount(filereader.lastNumberInclusive+1+2);
         int k = 0;
         for (int i = 0; i <= filereader.lastNumberInclusive; i++)
         {
             Vector3 vtemp;
         vtemp.x = -200 - 1 * (float)i + filereader.lastNumberInclusive / 2;
         vtemp.y = sfy* filereader.var[0, i];
             vtemp.z = 200;
             lineRenderer.SetPosition(k, vtemp);
             k++;
         }

         int j = filereader.frameCount;
         Vector3 vPos = new Vector3 (-200 - 1*j + filereader.lastNumberInclusive / 2, sfy *                          filereader.var[0, j], 200);
         Sphere.position = vPos;
         text1.transform.position = vPos;
         text1.text = j.ToString() + " " + filereader.var [0, j].ToString("0");
     }

The latter function starts running immediately, the prior starts after a certain timespan. Can anybody tell me why my second line renderer's appearance makes my other line renderer disappear?

Thanks!