How do I highlight all available paths with Dijkstra's algorithm on a square tile-based map?

I asked this question before, I accepted an answer, because it worked with the variables I tested with, didn't check if it worked when you change them.

Anyway, when I click on a character I want to see how far it can move on a square tile based map, with x amount of movement points that it has got (like Fire Emblem games). 1 movement point allows you to move one tile to the right, left, top or bottom.

Here is my ValidMoves class which should be finding all paths, but I believe it has problems with the movePoints argument and nextMoveCost in the GetValidMoves function

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class ValidMoves : MonoBehaviour 
 {
     public List<Node> validMoves = new List<Node>();
     void Start()
     {
         validMoves.Clear();
         //Tiles initialized and startTile is the current Tile
     }
     public void GetValidMoves(Node startTile, int movePoints)
     {
         validMoves.Add(startTile);
         for (int i = 0; i < startTile.neighbours.Count; i++)
         {        
 
             if(!GameManager.instance.tileArray[startTile.neighbours[i].x, startTile.neighbours[i].y].GetComponent<ClickableTile>().isWalkable)
                 continue;
             int nextMoveCost = movePoints - (int) GameManager.instance.tileArray[startTile.neighbours[i].x, startTile.neighbours[i].y].GetComponent<ClickableTile>().movementCost; 
                 if (nextMoveCost >= 0 && !validMoves.Contains(startTile.neighbours[i]))
                     GetValidMoves(startTile.neighbours[i], nextMoveCost);
         }
     }
     public void clearMoves()
     {
         
         validMoves.Clear();
     }
 }
 

validMoves is a list of my class Node, which contains information about each tile, such as it's position, and a list of the class Node called neighbours (the tiles that are connected to it).

 using UnityEngine;
 using System.Collections.Generic;
 
 public class Node 
 {
     public List<Node> neighbours;
     public int x;
     public int y;
     
     public Node() 
     {
         neighbours = new List<Node>();
     }
     
     public float DistanceTo(Node n) 
     {
         if(n == null) {
             Debug.LogError("WTF?");
         }
         
         return Vector2.Distance(
             new Vector2(x, y),
             new Vector2(n.x, n.y)
             );
     }
     
 }
 

GameManager.instance.tileArray is an array of all tiles (GameObject), it's scripts contain the movement cost of the tile (the amount of movePoints needed to walk onto it) and other info. Eventually I will make class Node accessible through the tileArray, but I just haven't gotten around to doing so yet.

The function only works well when the character has either 1 or 2 movement point. When it has more than that, you can see similar patterns and you can notice that not all tiles are being accessed.

Here are some examples:

2 movement points: http://i.imgur.com/o4XrqgI.jpg

3 movement points: http://i.imgur.com/MGX57Qd.jpg

6 movement points: http://i.imgur.com/cyMccSb.jpg

Any help would be appreciated.