shortcode excerpt loaded before all other content

I am using the following function to load one custom post type post by shortcode. Nice and easy to add to a Gutenberg block. But somehow the title loads where I add the shortcode and the excerpt loads at the beginning of the page before all other blocks. Any ideas why?

Here is the code

<?php
// [imwz-random-posts] shortcode
add_shortcode('imwz-random-posts','imwz_rand_posts');
function imwz_rand_posts() { 
 
$args = array(
    'post_type' => 'molecule',
    'orderby'   => 'rand',
    'posts_per_page' => 1, 
    );
 
$random_molecules = new WP_Query( $args );
	$rndmom = ''; 
if ( $random_molecules->have_posts() ) {
	

	while ( $random_molecules->have_posts() ) :
			$random_molecules->the_post();
			$rndmom .= '<div>';
			$rndmom .= '<h3><a href="'. get_permalink() .'">'. get_the_title() .'</a></h3><p>' . the_excerpt() . '</p>';
			$rndmom .= '</div>';
	endwhile;
	
	
	/* Restore original Post Data */
	wp_reset_postdata();
} else {
 
$rndmom .= 'no posts found';
}
 
return $rndmom; 
}