Edit in JSFiddle

var popup = new wijmo.input.Popup('#popup');
var content = document.getElementById('content');
document.getElementById('showPopup').addEventListener('click', function (e) {
  content.innerHTML = "Popup1";
  popup.hidden.addHandler(function (s, e) {
    content.innerHTML = "Popup2";
    popup.show();
  });
  popup.show();
});

document.getElementById('showPopup_wa').addEventListener('click', function (e) {
  content.innerHTML = "Popup1";
  popup.hidden.addHandler(function (s, e) {
    // 回避方法
    window.setTimeout(function () {
      content.innerHTML = "Popup2";
      popup.show();
    }, 500);
  });
  popup.show();
});

<button id="showPopup">Popupを表示</button>
<button id="showPopup_wa">Popupを表示（回避方法）</button>
<div id="popup">
  <p id="content"></p>
  <div class="wj-dialog-footer">
    <button class="wj-hide">閉じる</button>
  </div>
</div>