Turn-based strategy possible moves issue

I'm making a turn-based strategy game similar to advance wars. I've implemented a BFS algorithm that whenever a unit is selected, all the possible tiles it can go too will be highlighted. The tiles are prefabs that are dragged onto the scene and I have a tile manager script that locks them into coordinates (0,0), (1,0), (2,0) etc.

The issue I'm having is that some tiles are not highlighting when they should be. At first I thought this was an issue with my BFS algorithm (it still could be) but what I noticed that for the tiles that didn't highlight correctly if I remove them from the scene and then re-add them it would work until I restarted Unity.

BFS algorithm

 public override List<GameObject> getReachableTiles(GameObject currentTile, int moves) {
         currentTile = tm.GetTileAt ((int)currentTile.transform.position.x, (int)currentTile.transform.position.y).gameObject;
         List<GameObject> tempTileList = new List<GameObject>();
         if (!adjacentTiles.Contains(currentTile)) {
             adjacentTiles.Add (currentTile);
         }
         if (tm.GetTileAt (((int)currentTile.transform.position.x -1), (int)currentTile.transform.position.y) != null
             && (!adjacentTiles.Contains(tm.GetTileAt((int)currentTile.transform.position.x -1, (int)currentTile.transform.position.y).gameObject))){ //Check for tile left of current
             tempTileList.Add(tm.GetTileAt (((int)currentTile.transform.position.x -1), (int)currentTile.transform.position.y).gameObject);
             Debug.Log("Check Left");
         }
         if (tm.GetTileAt (((int)currentTile.transform.position.x +1), (int)currentTile.transform.position.y) != null
             && (!adjacentTiles.Contains(tm.GetTileAt((int)currentTile.transform.position.x +1, (int)currentTile.transform.position.y).gameObject))){ //Check for tile right of current
             tempTileList.Add(tm.GetTileAt (((int)currentTile.transform.position.x +1), (int)currentTile.transform.position.y).gameObject);
             Debug.Log("Check Right");
         }
         if (tm.GetTileAt (((int)currentTile.transform.position.x), ((int)currentTile.transform.position.y -1)) != null
             && (!adjacentTiles.Contains (tm.GetTileAt((int)currentTile.transform.position.x, (int)currentTile.transform.position.y-1).gameObject))){ //Check for tile below of current
             tempTileList.Add(tm.GetTileAt ((int)currentTile.transform.position.x, ((int)currentTile.transform.position.y -1)).gameObject);
             Debug.Log("Check Down");
         }
         if (tm.GetTileAt (((int)currentTile.transform.position.x), ((int)currentTile.transform.position.y +1)) != null
             && (!adjacentTiles.Contains (tm.GetTileAt((int)currentTile.transform.position.x, (int)currentTile.transform.position.y+1).gameObject))){ //Check for tile Above of current
             tempTileList.Add(tm.GetTileAt ((int)currentTile.transform.position.x, ((int)currentTile.transform.position.y +1)).gameObject);
             Debug.Log("Check Up");
         }
         if (moves > 0) {
             foreach(GameObject tiles in tempTileList) {
                 getReachableTiles (tiles, moves-1);
             }
             return adjacentTiles;
         }
         else {
             return adjacentTiles;
             }

Update function that changes the colour of the tiles for the possible moves of selected unit

 protected virtual void Update () {
         if (selected) {
             renderer.material.color = isSelected;
             possibleMoves = this.getReachableTiles (this.gameObject, this.getMove());
             foreach (GameObject possmove in possibleMoves)
             {
                 possmove.renderer.material.color = Color.gray;
 
             }
 
         }
         else {
             renderer.material.color = notSelected;
         }
     }