Cave generation code. At low fill percentage, it seems the upper right is empty

Hello!

I have a code that generates cave. I followed Sebastian Lague's tutorial.

Plug this onto something and set the following variables:

Width = 128 Height = 72 Fill Percent = 50 Seed = null Use Random Seed = true Smoothness = 4 Edge Thickness = 2

 using UnityEngine;
 using System;
 using System.Collections;
 
 public class TerrainGeneration : MonoBehaviour {
 
     public int width, height;
     [Range (0, 100)]
     public int fillPercent;
     private enum Cubes
     {
         No,
         Yes
     };
     private Cubes [,] map;
     public string seed;
     public bool useRandomSeed;
     public int smoothness;
     public int edgeThickness;
     
     int GetNeighbors (int x, int y) {
         int neighbors = 0;
         for (int x2 = x - 1; x2 < x + 2; x2 ++)
         {    
             for (int y2 = y - 1; y2 < y + 2; y2 ++)
             {
                 if (x2 != x || y2 != y)
                 {
                     if (x2 > -1 && x2 < width && y2 > -1 && y2 < height)
                     {
                         if (map [x2, y2] == Cubes.Yes)
                         {
                             neighbors ++;
                         }
                     }
                     else
                     {
                         neighbors ++;
                     }
                 }
             }
         }
         return neighbors;
     }
     
     void Update () {
         if (Input.GetKeyDown (KeyCode.Space))
         {
             CreateGrid ();
         }
     }
     
     void CreateGrid () {
         map = new Cubes [width, height];
         PlaceHoles ();
     }
     
     void PlaceHoles () {
         if (useRandomSeed == true)
         {
             seed = Time.time.ToString ();
         }
         System.Random prng = new System.Random (seed.GetHashCode());
         for (int x = 0; x < width; x ++)
         {
             for (int y = 0; y < height; y ++)
             {
                 if (x < edgeThickness || x > width - edgeThickness - 1 || y < edgeThickness || y > height - edgeThickness - 1)
                 {
                     map [x, y] = Cubes.Yes;
                 }
                 else if (prng.Next (0, 100) < fillPercent)
                 {
                     map [x, y] = Cubes.Yes;
                 }
             }
         }            
         for (int s = 0; s < smoothness; s ++) 
         {
             SmoothMap ();
         }
     }
     
     void SmoothMap () {
         for (int x = 0; x < width; x ++)
         {
             for (int y = 0; y < height; y ++)
             {    
                 int neighbors = GetNeighbors (x, y);
                 if (neighbors > 4)
                 {
                     map [x, y] = Cubes.Yes;
                 }
                 else
                 {
                     map [x, y] = Cubes.No;
                 }
             }
         }
     }
     
     void OnDrawGizmos () {
         for (int x = 0; x < width; x ++)
         {
             for (int y = 0; y < height; y ++)
             {
                 if (map != null)
                 {
                     if (map [x, y] == Cubes.No)
                     {
                         Gizmos.color = Color.green;
                     }
                     if (map [x, y] == Cubes.Yes)
                     {
                         Gizmos.color = Color.red;
                     }
                     Vector3 pos = new Vector3 (x - width / 2 + 0.5f, y - height / 2 + 0.5f, 0);
                     Gizmos.DrawCube (pos, Vector3.one);
                 }
             }
         }
     }
 }

At 50%, it is clear that it is only developing at the lower left. EDIT

Since my last question I started over, and I have progressed a lot considering it is working. It just looks a little strange that's all. Like it has a seam.