Custom theme on multisite has issues with standard loop output

I have resolved this issue after reviewing a get_posts() function that was running in a template partial that was not using setup_postdata( $post ) at the start of the foreach and closing out with a wp_reset_postdata() after the foreach had completed.

This get_posts() was corrupting the main loop array and causing it to fail on page.php and single.php.

Fixed get_posts function

// Simplified for ease of reading
$args = array(
  'post_type' => 'post',
  'post_status' => 'publish',
  'numberposts' => 1,
);
$posts = get_posts( $args );

<?php if ( $posts ) : ?>
  <?php foreach ( $posts as $post ) : setup_postdata( $post ); ?>
  <!-- Post Content Output -->
  <?php endforeach; wp_reset_postdata(); ?>
<?php endif; ?>