unnecessary link using shortcode

sorry that I'm asking here everyday..

question about a plugin Marketpress

I wrote down this code

<div class="medium-6 columns">
  <p><?php mp_product_image(true, 'single', null); ?></p>
</div>

but when I check on browser (checked on chrome, firefox)

<div class="medium-6 columns">
  <p><a id="product_image-38" class="mp_product_image_link mp_lightbox" rel="lightbox" href="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg"><img width="200" height="191" src="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg" class="alignleft mp_product_image_single wp-post-image" alt="sample-image" itemprop="image" title="View Larger Image »"></a>
  </p>
  <a id="product_image-38" class="mp_product_image_link mp_lightbox" rel="lightbox" href="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg"></a>
</div>
<a id="product_image-38" class="mp_product_image_link mp_lightbox" rel="lightbox" href="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg">
</a>

added 2 'a' link automatically when I use shortcode function (other shortcode like [mp_list_categories] too)

I want

<div class="medium-6 columns">
  <p><a id="product_image-38" class="mp_product_image_link mp_lightbox" rel="lightbox" href="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg"><img width="200" height="191" src="http://entraide.fe-labs.net/portal/fe03/wp-content/uploads/sites/6/2013/12/sample-image.jpg" class="alignleft mp_product_image_single wp-post-image" alt="sample-image" itemprop="image" title="View Larger Image »"></a>
  </p>
</div>

I need to fix something on template-function.php ?

sorry for my poor English, thanks in advance