CKEditor disappears if loading a page twice using a ajax call

I am calling a same jsp page twice using a Ajax call.  But getting the following error and it is displaying the textarea and not the CKEditor:
TypeError: a is undefined
TypeError: a.ui.space(...) is null

My Code is:

<script>
      // Replace the <textarea id="editor1"> with a CKEditor
      // instance, using default configuration.
      $( document ).ready(function() {
          if (CKEDITOR.instances['questionText']) {
              CKEDITOR.remove(CKEDITOR.instances['questionText']);
          }

          CKEDITOR.replace('questionText', {
              enterMode : CKEDITOR.ENTER_BR,
              shiftEnterMode: CKEDITOR.ENTER_BR,
              coreStyles_bold: { element: 'b' },
              coreStyles_italic: { element: 'i' }
          });
      });
           if (CKEDITOR.instances['questionText']) {
           CKEDITOR.instances['questionText'].on('change',function() {
           $('#questionText').val(CKEDITOR.instances['questionText'].getData());

           });
           }

  </script>

Please help me. I am struggling on it since 5 days. :(