php - Why is query_posts causing an infinite loop here?

I have looked around for information explaining my issue but found none. I have a loop which supposedly should list all children categories of 'personnel'. For some reason the loop restarts infinitely. I have checked and it goes out of both the foreach and while loop but still manages to keep looping. Any ideas?

I'm calling the function here:

// Personnel listing
upp_loop('Personal', 'personnel-preview', '<section class="res-table">', '</section>');
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And this is the code generating the posts:

// Loop through children (To make headers)
                $cats = get_categories('child_of=' . $catID . '&orderby=count&order=DESC');

                foreach ($cats as $cat) :

                $args = array(
                    'cat' => $cat->term_id
                );
                $query = new WP_query($args);

                    if ($query->have_posts()) :
                        // Echo the Category name
                        ?> <h2><?php echo $cat->name; ?></h2> <?php

                        // List all children
                        while($query->have_posts()) :
                            $query->the_post();
                                if (has_post_thumbnail()) {
                                    $img = wp_get_attachment_image_src( get_post_thumbnail_id( $post->ID ), 'single-post-thumbnail' );
                                }
                                else {
                                    $img[0] = get_template_directory_uri() . "/img/program-default.png";
                                }?>
                                    <a href="<?php the_permalink(); ?>" class="res-td">
                                        <img src="<?php echo $img[0] ?>" alt="<?php the_title(); ?>"/>
                                        <h2><?php the_title() ?></h2>
                                    </a>
                                <?php
                        endwhile;
                    endif;
                endforeach;
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