Posts repeat after all posts have been loaded

Hi, I would like to buy the premium version of your plugin to take advantage of the “Load More” option, but I just want to make sure I get it working using the free version first.

I am running into an issue where once you scroll down the page, it loads the next posts, but then if you scroll further, it loads the same posts again.

http://50.87.248.182/~homecolu/

Any help on this would be much appreciated.

The query I am using is below:

if ( get_query_var('paged') ) {
  $paged = get_query_var('paged');
} elseif ( get_query_var('page') ) {
  $paged = get_query_var('page');
} else {
  $paged = 1;
}

$list_args = array(
  'post_type' => 'property',
  'posts_per_page' => 3,
  'meta_key' => 'open_house_date',
  'orderby' => 'meta_value_num',
  'order' => 'ASC',
  'paged' => $paged,
  'meta_query' => array(
     array(
       'key'     => 'open_house',
       'value'   => 'yes',
       'compare' => '=',
     ),
  )
);
$list_query = new WP_Query( $list_args ); ?>
<?php if ( $list_query->have_posts() ) : ?>
  <div class="open-house-list">
    <?php while ( $list_query->have_posts() ) : $list_query->the_post(); ?>
    <div class="open-house-item">
       <!--post content here-->
    </div>
    <?php endwhile; ?>
<?php if (  $list_query->max_num_pages > 1 ) : ?>
  <nav id="open-house-pagination">
    <?php next_posts_link('Older »', $list_query->max_num_pages ) ?>
    <?php previous_posts_link( 'Newer posts »', $list_query->max_num_pages);?>
  </nav>
<?php endif; ?>
</div>
<?php wp_reset_query(); ?>
<?php endif; ?>