Using the_post_thumbnail resets current loop item ID

Question

I'm facing a very strange issue when displaying custom loop items (from a new WP_Query) on a static homepage template.

Each item has a thumbnail, title, and some meta info. Every time I use the_post_thumbnail() to show the featured image the current post ID from the loop is set to the page ID that is used for the static page template.

Everything I output after the featured image shows the current page properties. If I move the featured thumbnail code at the end of each loop everything I output before shows up correctly.

If I use wp_get_attachment_image_src(get_post_thumbnail_id()) to construct the img tag the issue doesn't appear anymore, but I need the_post_thumbnail() so I can hook later to change the sizes attribute.

Any ideas why this happens?

UPDATE (code added):

This is the code for the static template page:

<?php

/**
 * Template Name: Magazine homepage
 *
 * @link https://codex.wordpress.org/Template_Hierarchy
 *
 */

get_header();

do_action('ultraquick_after_header');

if (is_paged()) {
    if (function_exists('ultraquick_breadcrumbs')) {
        ultraquick_breadcrumbs();
    }
}

if (is_front_page() && !is_paged() && in_array(get_theme_mod('ultraquick_featured'), array('featured-5', 'featured-6'))) : ?>

    <div class="featured">
        <div class="featured-wrapper">
            <?php get_template_part('template-parts/featured'); ?>
        </div>
    </div>
    <!--/.featured-->

<?php endif; ?>

<div id="content" class="site-content">

    <div id="primary" class="content-area">

        <main id="main" class="site-main">

            <?php if (!is_paged()) { // If on the first page show template contents 
            ?>
                <div class="magazine-homepage-widgets">

                    <?php if (is_active_sidebar('homepage-1')) { ?>
                        <div class="magazine-homepage-posts homepage-1">
                            <?php dynamic_sidebar('homepage-1'); ?>
                        </div>
                    <?php } ?>

                </div>

            <?php }

            if (is_front_page()) { // Only if page is set as static homepage

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

                $posts = new WP_Query(array('post_type' => 'post', 'paged' => $paged));
                $wp_query = $posts; // Replace main query

                if (is_paged() && have_posts()) { // If on the second page of the static homepage
                    /* Start the Loop */
                    while (have_posts()) :
                        the_post();

                        /*
                        * Include the Post-Type-specific template for the content.
                        * If you want to override this in a child theme, then include a file
                        * called content-___.php (where ___ is the Post Type name) and that will be used instead.
                        */
                        get_template_part('template-parts/content', get_post_type());

                    endwhile;
                }
                wp_reset_postdata();

                // show pagination.
                get_template_part('include/pagination');
            }
            ?>

        </main><!-- #main -->
    </div><!-- #primary -->

    <?php get_sidebar(); ?>

</div><!-- #content -->
<?php get_footer();

And this is the code for the widgets I'm using:

$custom_query_args = array(
            'post_type' => 'post',
            'posts_per_page' => $number_posts,
            'post_status' => 'publish',
            'ignore_sticky_posts' => $ignore_sticky,
            'category__in' => $block_category,
            'tag__in' => $block_tag,
            'order' => $order,
            'orderby' => $orderby,
        );

        $custom_query = new WP_Query(apply_filters('widget_block_posts_args', $custom_query_args));
        if ($custom_query->have_posts()) {
            $count = 0;

            echo str_replace('class="', 'class="' . $layout_block . ' ', $args['before_widget']);

            $widget_title = ultraquick_widget_magazine_title($block_category, $block_tag, $title);
            if ($widget_title) { ?>
                <div class="posts-block-title-wrapper">
                    <?php
                    echo $args['before_title'];
                    echo '<div class="posts-block-title">';
                    if (!$widget_title['link']) {
                        echo  $widget_title['title'];
                    } else {
                    ?>
                        <a rel="term" href="<?php echo esc_url($widget_title['link']); ?>"><?php echo esc_html($widget_title['title']); ?></a>
                    <?php
                    }
                    echo '</div>';
                    echo $args['after_title'];
                    ?>
                </div>
            <?php } ?>

            <div class="posts-block <?php echo esc_attr($instance['layout']); ?> col-<?php echo esc_attr($instance['column']); ?>">

                <?php
                while ($custom_query->have_posts()) : $custom_query->the_post();
                    $count++;
                    if ((strpos($layout, 'first-row-large') !== false) && $count == 1) : $large = "article-large";
                    else : $large = "article-small";
                    endif; ?>
                    <article <?php post_class($large); ?>>

                        <div class="archive-thumbnail">
                            <?php the_post_thumbnail(); ?>
                        </div>

                        <div class="archive-meta">
                            <div class="entry-header">
                                <?php if ($meta) { ?>
                                    <div class="entry-meta">
                                        <?php
                                        ultraquick_posted_on();
                                        ultraquick_posted_by();
                                        echo '<br/>';
                                        ultraquick_posted_in();
                                        ultraquick_post_comments();
                                        ?>
                                    </div>
                                <?php } ?>

                                <?php the_title('<h2 class="entry-title"><a href="' . esc_url(get_permalink()) . '" rel="bookmark">', '</a></h2>'); ?>

                                <?php if ($excerpt) { ?>
                                    <div class="entry-summary">
                                        <?php
                                        the_excerpt(sprintf(
                                            wp_kses(
                                                /* translators: %s: Name of current post. Only visible to screen readers */
                                                __('Continue reading<span class="screen-reader-text"> "%s"</span>', 'ultraquick'),
                                                array(
                                                    'span' => array(
                                                        'class' => array(),
                                                    ),
                                                )
                                            ),
                                            get_the_title()
                                        ));
                                        ?>
                                    </div><!-- .entry-summary -->
                                <?php } ?>
                            </div>
                        </div>

                    </article>
                <?php
                endwhile; ?>

            </div> <!-- .posts_block -->

        <?php echo $args['after_widget'];

            // Reset the global $the_post as this query will have stomped on it
            wp_reset_postdata();
        } // end if posts
    }