wrong calculation of dialog content width and height with css theme "start"

It seems that problem occurs with theme "start" because I could not make a jsFiddle showing it.

My dialog is very simple, At the click of the user I load content from the server.

HTML code :

<div id="dialog"></div>
<div>
    <li>
        <a href="configuration.do" class="dialogify" title="Configuration de l'application">Configuration</a>
    </li>
</div>

JS code :

    $("#dialog").dialog({
        autoOpen: false
    });
    $(".dialogify").on("click", function(e) {
        var title = this.title;
        e.preventDefault();
        $("#dialog").html("");
        $("#dialog").dialog("option", "title", "Loading...").dialog("open");
        $("#dialog").load(this.href, function() {
            $(this).dialog("option", "title", title);
        });
    });

The issue is that each time I resize the dialog, the content of the dialog loses space.

The workaround I found is to set the following CSS :

#dialog {
    padding: 3.5px;
}

Then the content of the dialog is correctly resized.