Undo and Redo Canvas Not Working as Expected

I have a canvas with an addable objects, as well as Undo and Redo buttons. As you can see in my example, I'm able to undo/redo 1 time but things break; by this I mean I can add an object and remove it but if for example I move the added object and hit undo, it should move to where I had it previously but instead it disappears from the canvas.

I'm using fabric.js 1.7.22.

My Code:

var canvas = this.__canvas = new fabric.Canvas('canvas', {
  backgroundColor: 'grey',
  centeredScaling: true
});
canvas.setWidth(400);
canvas.setHeight(600);

canvas. preserveObjectStacking = true;

// Add Text
function Addtext() {
  var text = new fabric.IText("Tape and Type...", {
    fontSize: 30,
    top: 10,
    left: 10,
    textAlign: "center",
  });
  canvas.add(text);
  canvas.centerObject(text);
  canvas.setActiveObject(text);
  text.enterEditing();
  text.selectAll();
  canvas.renderAll();
  canvas.isDrawingMode = false;
}

// Undo Redo
canvas.on('object:added',function(){
  if(!isRedoing){
    h = [];
  }
  isRedoing = false;
});

var isRedoing = false;
var h = [];
function undo(){
  if(canvas._objects.length>0){
   h.push(canvas._objects.pop());
   canvas.renderAll();
  }
}
function redo(){
  
  if(h.length>0){
    isRedoing = true;
   canvas.add(h.pop());
  }
}

<script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN"
    crossorigin="anonymous"></script>
  <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm"
    crossorigin="anonymous">
  <script src="https://cdnjs.cloudflare.com/ajax/libs/fabric.js/1.7.22/fabric.min.js"></script>
  <link href="https://fonts.googleapis.com/icon?family=Material+Icons" rel="stylesheet">
  
        <a href="#" class="btn btn-dark" onclick="Addtext()">Add Text</a>

<button onclick="undo()" type="button" class="btn btn-sm btn-dark">
        <i class="material-icons">undo</i>
      </button>

      <button onclick="redo()" type="button" class="btn btn-sm btn-dark">
        <i class="material-icons">redo</i>
      </button>
      
      <canvas id="canvas"></canvas>

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