1. Open up admin/items.php and on line 823 right after:

sortgal: 1,

add:

id: <?php echo Filter::$id;?>,

2. Open up /admin/helper.php and on line 505 replace:

  /* == Sort Gallery == */
  if (isset($_POST['sortgal'])):
      $i = 0;
      foreach ($_POST['sorting'] as $v):
          $i++;
          $data['sorting'] = $i;
          $db->update(Items::gTable, $data,  array('id' => $v));
      endforeach;
  endif;

with:

  /* == Sort Gallery == */
  if (isset($_POST['sortgal'])):
      $i = 0;
      foreach ($_POST['sorting'] as $v):
          $i++;
          $data['sorting'] = $i;
          $db->update(Items::gTable, $data,  array('id' => $v));
      endforeach;
      if ($gallery = Items::getGalleryImages(Filter::$id)) :
          $db->update(Items::lTable, array('gallery' => serialize($gallery)), array('id' => Filter::$id));
      endif;
  endif;