Ignore the “carts” post type

<?php

// Add the following to your child theme's functions.php
add_filter( 'facetwp_is_main_query', function( $is_main_query, $query ) {
    if ( 'carts' == $query->get( 'post_type' ) || 1 === $query->get( 'numberposts' ) ) {
        $is_main_query = false;
    }
    return $is_main_query;
}, 10, 2 );