Issue with drag and dropping fields into regions (custom DS layout)

Hi,

I created a custom layout according to the explanation at http://drupal.org/node/1098068
The problem is that when I drag and drop any field into a region it always ends up in the first region (after ajax save) which in my case is the region "header". When I use the selects instead of the drag & drop, the fields move to the correct region.

I can't use the selects though because my fields need to be added to fieldsets within these regions (and you know you can only select to which region you want to assign a field and not the fieldsets within regions)

Here's the code for my custom template (altough I don't think that has anything to do with it):

3col_3row_equal_width.inc.inc

<?php
function ds_3col_3row_equal_width() {
  return array(
    'label' => t('Three column three row - Equal width'),
    'regions' => array(
      'header' => t('Header'),
      'first_left' => t('Left (first)'),
      'first_middle' => t('Middle (first)'),
      'first_right' => t('Right (first)'),
      'second_left' => t('Left (second)'),
      'second_middle' => t('Middle (second)'),
      'second_right' => t('Right (second)'),  
      'third_left' => t('Left (third)'),
      'third_middle' => t('Middle (third)'),
      'third_right' => t('Right (third)'),
      'footer' => t('Footer')       
    ),
    // Add this line if there is a default css file.
    'css' => TRUE,
  );
}
?>

3col_3row_equal_width.tpl.php

<div class="<?php print $classes;?> clearfix">

  <?php if (isset($title_suffix['contextual_links'])): ?>
    <?php print render($title_suffix['contextual_links']); ?>
  <?php endif; ?>
  
  <div class="ds-row-first ds-row">
    <?php if ($header): ?>
      <div class="ds-header<?php print $header_classes; ?>">
        <?php print $header; ?>
      </div>
    <?php endif; ?>  

    <?php if ($first_left): ?>
      <div class="ds-first-left<?php print $first_left_classes; ?>">
        <?php print $first_left; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($first_middle): ?>
      <div class="ds-first-middle<?php print $first_middle_classes; ?>">
        <?php print $first_middle; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($first_right): ?>
      <div class="ds-first-right<?php print $first_right_classes; ?>">
        <?php print $first_right; ?>
      </div>
    <?php endif; ?>           
  </div>
  
  <div class="ds-row-second ds-row">
    <?php if ($second_left): ?>
      <div class="ds-second-left<?php print $second_left_classes; ?>">
        <?php print $second_left; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($second_middle): ?>
      <div class="ds-second-middle<?php print $second_middle_classes; ?>">
        <?php print $second_middle; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($second_right): ?>
      <div class="ds-second-right<?php print $second_right_classes; ?>">
        <?php print $second_right; ?>
      </div>
    <?php endif; ?>           
  </div>  
  
  <div class="ds-row-third ds-row">
    <?php if ($third_left): ?>
      <div class="ds-third-left<?php print $third_left_classes; ?>">
        <?php print $third_left; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($third_middle): ?>
      <div class="ds-third-middle<?php print $third_middle_classes; ?>">
        <?php print $third_middle; ?>
      </div>
    <?php endif; ?> 
    
    <?php if ($first_right): ?>
      <div class="ds-third-right<?php print $third_right_classes; ?>">
        <?php print $third_right; ?>
      </div>
    <?php endif; ?>  
    
    <?php if ($footer): ?>
      <div class="ds-footer<?php print $footer_classes; ?>">
        <?php print $footer; ?>
      </div>
    <?php endif; ?>             
  </div>
  
</div>