Can't reprduce the issue as you described.
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Basic Window - jQuery EasyUI Demo</title>
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/default/easyui.css">
<link rel="stylesheet" type="text/css" href="https://www.jeasyui.com/easyui/themes/icon.css">
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.min.js"></script>
<script type="text/javascript" src="https://www.jeasyui.com/easyui/jquery.easyui.min.js"></script>
</head>
<body>
<div id="test-window-1" class="easyui-window" title="NORMAL" style="padding:0px;"></div>
<div id="test-window-2" class="easyui-window" title="BUG" style="padding:0px;"></div>
<div id="test-window-3" class="easyui-window" title="BUG" style="padding:0px;"></div>
<script>
$('.easyui-window').window({
collapsible: true,
minimizable: false,
maximizable: false,
closable: true,
closed: true
});
$(function() {
// Works fine
$('#test-window-1').window({ height: '200px', width: '200px' });
$('#test-window-1').window('vcenter');
$('#test-window-1').window('open');
// Bugged but after resize by user is working correctly
$('#test-window-2').window({ height: '200px', width: '200px' });
$('#test-window-2').window({ title: 'BUGGED' });
$('#test-window-2').window('vcenter');
$('#test-window-2').window('open');
// Works fine with changed title
$('#test-window-3').window({ title: 'NOT BUGGED' });
$('#test-window-3').window({ height: '200px', width: '200px' });
$('#test-window-3').window('vcenter');
$('#test-window-3').window('open');
});
</script>
</body>
</html>