Adding elements to a list is changing the initial values. Need help!

So I'm generating a maze and I want to create a list of adjacent cells to a specific cell. Here is my current code that's relevant to the problem:

 public static void AddFrontier(List<List<int>> frontier, List<int> loci,List<List<int>> maze, int size)
     {
         loci[0] += 1;
         FrontierCondition(frontier, loci, maze, size);
         loci[0] -= 2;
         FrontierCondition(frontier, loci, maze, size);
         loci[0] += 1;
         loci[1] += 1;
         FrontierCondition(frontier, loci, maze, size);
         loci[1] -= 2;
         FrontierCondition(frontier, loci, maze, size);
         loci[1] += 1;
     }
     public static void FrontierCondition(List<List<int>> frontier, List<int> loci, List<List<int>> maze, int size)
     {
         if (!frontier.Contains(loci) & !maze.Contains(loci))
         {
             if (loci[0] < size & loci[1] < size)
             {
                 frontier.Add(loci);
             }
         }
     }
 ... (generating maze walls and floor)
 var maze = new List<List<int>>();
         var frontier = new List<List<int>>();
         c = Random.Range(0,grid.Count);
         maze.Add(grid[c]);
         var loci = new List<int>
         {
             grid[c][0],
             grid[c][1],
         };
         Debug.Log(string.Format("{0},{1}", loci[0], loci[1]));
         AddFrontier(frontier, loci, maze, size);
         for (int e = 0; e < frontier.Count; e += 1)
         {
             Debug.Log(string.Format("{0},{1}", frontier[e][0], frontier[e][0]));
         }

It keeps messing up with the Z coordinate. Apparently, 19 - 1 is 5... The X coordinate is generated perfectly yet the Z is FUBAR'd constantly.