display posts with same taxonomy term

I’m trying to display 5 related posts in the loop, those related posts being posts that share the same taxonomy value. e.g. I have a custom taxonomy set up called venues thus each post has a venue taxonomy value assigned to it, so in each post I want to display 5 others posts that share the same taxonomy value (i.e. are at the same venue).
The code I have so far doesn’t work quite right:

<?php if ( have_posts() ) : while ( have_posts() ) : the_post(); ?>
<?php
$custom_terms = get_terms('venues');

foreach($custom_terms as $custom_term) {
    wp_reset_query();
    $args = array('post_type' => 'listings',
    'posts_per_page' => 5,
        'tax_query' => array(
            array(
                'taxonomy' => 'venues',
                'field' => 'slug',
                'terms' => $custom_term->slug,
            ),
        ),
     );

     $loop = new WP_Query($args);
     if($loop->have_posts()) {

        while($loop->have_posts()) : $loop->the_post(); ?>
        <div class="listing-title"><?php the_title(); ?></div>     
        <?php endwhile;
     }
}
?>
<?php wp_reset_query(); ?>
<?php endwhile; endif; ?>

It is successfully showing 5 posts, but they are just five posts from the same post type and not 5 posts that share the same taxonomy value in the loop. Any suggestions would be greatly appreciated!

Totally untested and I’m not 100% sure I understand your question, but this should (in theory) get 5 posts that share any of the same venues as the current post. I would probably suggest adding some Transients to this so that you aren’t constantly running queries.

If it doesn’t work, I suspect the syntax of my tax query is a little off. It always gets me because it is an array of arrays.

//get the post's venues
$custom_terms = get_terms('venues');

if( $custom_terms ){

    // going to hold our tax_query params
    $tax_query = array();

    // add the relation parameter (not sure if it causes trouble if only 1 term so what the heck)
    if( count( $custom_terms > 1 ) )
        $tax_query['relation'] = 'OR' ;

    // loop through venues and build a tax query
    foreach( $custom_terms as $custom_term ) {

        $tax_query[] = array(
            'taxonomy' => 'venues',
            'field' => 'slug',
            'terms' => $custom_term->slug,
        );

    }

    // put all the WP_Query args together
    $args = array( 'post_type' => 'listings',
                    'posts_per_page' => 5,
                    'tax_query' => $tax_query );

    // finally run the query
    $loop = new WP_Query($args);

    if( $loop->have_posts() ) {

        while( $loop->have_posts() ) : $loop->the_post(); ?>

        <div class="listing-title"><?php the_title(); ?></div>     
        <?php endwhile;
    }

    wp_reset_query();

}?>