My friend i cannot give you access cause its an intranet site.
But i dig it a liitle and i see that in your html/com_content/article/default.php, and specific in line 81 there is a code that has the problem.
<!-- Intro text -->
<?php if (isset ($this->item->introtext)) : ?>
<div class="intro-text">
<?php echo $this->item->introtext; ?>
</div>
<?php endif; ?>
<!-- // Intro text -->
This code is not needed! It duplicates the introtext because later on the default.php in line 134 there is the:
<?php echo $this->item->text; ?>
the item->text is a field that already has checked if the the introtext is set to on or off and has populated the right content.
Problem fixed for me. I deleted the first pile of code... But in future updates the issue will still be there. you should check it.