Strange issue with undefined ngmodel

Question

For some strange reason, the value of the ng-model is undefined most of the time, then it randomly has value.

My view code is:

<div data-ng-controller="contentModalCtrl as vm">
  <div class="modal-header">
    <h3 class="modal-title model-title">Content stuff</h3>
  </div>
  <div class="modal-body">
    <text-angular ta-toolbar="[['indent', 'outdent', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'ol', 'quote', 'bold','italics']]" ng-model="vm.data.text" required></text-angular>
  </div>
  <div class="modal-footer">

    <button type="submit" class="btn" data-ng-disabled="!vm.data.text" data-ng-click="vm.save()">Submit</button>
    <button class="btn" data-ng-click="vm.close()">Close</button>

  </div>

</div>

My controller looks like this:

    angular.module("app").controller("contentModalCtrl", function($scope, ngDialog) {
        "use strict";
        var vm = this;
        vm.data = {
          text: ""
        };
     vm.close = function() {
        ngDialog.close();
      };

  vm.save = function() {

    console.log(vm.data.text);
  // code used to process data.text
    ngDialog.close();
  };

});

Sometimes the ng-model has value, most of the time it doesn't. The odd part is if I continuously type random things into the text area, the ng-model eventually picks up the typed values. I am not sure if this is a text-angular issue or a NgDialog issue. Does anyone know what is going on?