see my notes in comments. I’m not sure if this will cause the problem your having or not.
if ( $subservice->have_posts() ) : ?>
<?php while ( $subservice->have_posts() ) : $subservice->the_post(); $count++?>
<section class="pp-section" id="section<?php echo $count; ?>"><!-- no end tag -->
<div class="fadearound"><!-- no end tag -->
<div class="bgfadearound loading" style="background-image: url('<?php bloginfo('stylesheet_directory'); ?>/assets/img/bg_01.jpg');"></div>
<div class="container-right"><!-- no end tag -->
<?php
$related_posts = get_field('reference_1');
if( $related_posts ): // no endif ?>
<ul>
<?php foreach( $related_posts as $p ): // variable must NOT be called $post (IMPORTANT) ?>
<li>
<a href="<?php echo get_permalink( $p->ID ); ?>"><?php echo get_the_title( $p->ID ); ?></a>
<span>Custom field from $post: <?php the_field('author', $p->ID); ?></span>
</li>
<?php endforeach; ?>
</ul>
<?php endwhile; ?>
<?php endif; wp_reset_query(); ?>
