culling issues on dynamically generated mesh

i am using a mesh to display gun trails in my game. i am updating only the vertex positions when a new trail is created, uvs and triangles are consistent.

the problem is that it disappears at certain camera angles / positions, i think the issue is occlusion / frustrum culling.

in 2017.2 i could solve this by disabling occlusion culling in the mesh renderer component.

unfortunately, as of 2017.3 the mesh is still culled.

what is the correct way to solve this?

can i disable culling for the object or can i update the culling box via script at runtime?

script:

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class gunTrail : MonoBehaviour {
     [RequireComponent(typeof(MeshFilter))]
     public int maxtrails = 6;
     public float trailWidth = .01f;
     int nextTrail = 0;
     bool Trailchanges = false;
     Vector3[] trailstart;
     Vector3[] traildirection;
 
     Vector3[] vertices;
     Vector2[] uvs;
     int[] triangles;
 
     Mesh mesh;
 
     void Start () {
         mesh = new Mesh ();
         GetComponent<MeshFilter> ().mesh = mesh;
 
         trailstart        = new Vector3[maxtrails];
         traildirection     = new Vector3[maxtrails];
 
         vertices = new Vector3[maxtrails*3]; 
         triangles = new int[maxtrails*3*2];
         uvs = new Vector2[vertices.Length];
 
         for (int i = 0; i < maxtrails; i++) {
             vertices [i * 3 + 0] = new Vector3 (0, -10, 0);
             vertices [i * 3 + 1] = new Vector3 (0, -10, 0);
             vertices [i * 3 + 2] = new Vector3 (0, -10, 0);
             triangles [i * 6 + 0] = i * 3;
             triangles [i * 6 + 1] = i * 3 + 1;
             triangles [i * 6 + 2] = i * 3 + 2;
             triangles [i * 6 + 3] = i * 3;
             triangles [i * 6 + 4] = i * 3 + 2;
             triangles [i * 6 + 5] = i * 3 + 1;
             uvs [i * 3 + 0] = new Vector2 (0f, 0f);  //wil be first start point
             uvs [i * 3 + 1] = new Vector2 (1f, .5f); //will be end point
             uvs [i * 3 + 2] = new Vector2 (0f, 1f);  //will be 2nd start point
         }
 
         mesh.vertices = vertices;
         mesh.uv = uvs;
         mesh.triangles = triangles;
 
     }
 
     void FixedUpdate () {
         if (Trailchanges) {
             mesh.vertices = vertices;
             //mesh.triangles = triangles;
             Trailchanges = false;
         }
     }
     public void makeTrail(Vector3 start, Vector3 direction){
         trailstart [nextTrail] = start;
         traildirection [nextTrail] = direction;
         if (false) {
             vertices [nextTrail * 3] = start;
             vertices [nextTrail * 3 + 1] = start + direction;
             vertices [nextTrail * 3 + 2] = start + new Vector3 (0f, trailWidth, 0f);
         } else {
             vertices [nextTrail * 3] = start + direction;
             vertices [nextTrail * 3 + 1] = start;
             vertices [nextTrail * 3 + 2] = start + direction + new Vector3 (0f, trailWidth, 0f);
         }
 
         Trailchanges = true;
         nextTrail++;
         nextTrail = nextTrail % maxtrails;
     }
 }