Issue showing most popular posts

Hiya all, hope you’re well. I run this site (www.coolsmartphone.com) and, on the upper right, there’s a section for “most popular posts in the last week”. It uses this code..

<?php $loop = new WP_Query( array( 'meta_key' => 'Views', 'orderby' => 'meta_value', 'year' => date( 'Y' ), 'w' => date( 'W' ), 'posts_per_page' => 3 ) ); ?>

..however, every now and then (like today) it’ll show random older posts then it’ll clear itself the next day. I can’t find a reason for it. Does anyone know why this is ? I’ve Googled to heck and can’t find an explanation.