Dragging & dropping disabled blocks is buggy

Although this has been said fixed (#649982: Improve the drag-drop handling for dashboard customisation) the layout is still very strange. Have a look at the screenshot. This happens in at least Chrome and IE8, after a few drags/drops. To reproduce: drag a block from the disabled region and drop it in that same region (disabled). Repeat this a few times and more and more things seem to break.

Looking at the rendered sourcecode (after dragging) I see a lot of strange things:

<div class="region disabled-blocks clearfix ui-sortable">
  <div id="block-comment-recent" class="disabled-block block block-comment-recent module-comment delta-recent">
    <h2>Recent comments</h2>
    <div class="content"></div>
  </div>
<div id="block-user-online" class="block block-user-online module-user delta-online" style="">
  <div id="block-user-online" class="block block-user contextual-links-region">
    <h2>Who's online</h2>
    <div class="contextual-links-wrapper contextual-links-processed"><a class="contextual-links-trigger" href="#">Configure</a><ul class="contextual-links"><li class="block-configure first last"><a href="/drupal7/?q=admin/structure/block/manage/user/online/configure&amp;destination=admin/dashboard/block-content/user/online">Configure block</a></li>
      </ul>
    </div>
    <div class="content">
      <p>There is currently 1 user online.</p>
      <div class="item-list"><ul><li class="first last"><a href="/drupal7/?q=user/1" title="View user profile." class="username" xml:lang="" about="/drupal7/?q=user/1" typeof="sioc:UserAccount" property="foaf:name">BarisW</a></li></ul>
      </div>
    </div>
  </div>
</div>

[..etc..]

So we see two nested DIV's with the same ID. And the class .disabled-block is missing.