Custom Loop Using Shortcode in Custom Page Template

The problem seems to be in the Loop. Inside the Loop you are not incrementing the $the_query. You may change the code for the Loop as below:

// The Loop
if ( $the_query->have_posts() ) {
    while ( $the_query->have_posts() ) {
        $the_query->the_post();  // Add this line to fix the issue
        smr_product_the_frontend_item();
    }
} else {
    // no posts found
}