Loading twice WooCommerce thankyou page would duplicate Conversion tracking?

You can use order custom meta data to avoid duplicated Conversion tracking as follows:

add_action( "woocommerce_thankyou", "pixel_analytics_conversion_track_script", 20 );if ( ! function_exists( 'pixel_analytics_conversion_track_script' ) ) {    function pixel_analytics_conversion_track_script( $order_id ) {        // Avoid if pixel analytics conversion track script has been run before        if ( $order_id > 0 && 'done' !== get_post_meta( $order_id, '_pixel_tracking', true ) ) {            $order = wc_get_order( $order_id );                        if ( is_a($order, 'WC_Order') ) {                $order_id               = $order->get_id(); // order id                $order_key              = $order->get_order_key(); // order key                $order_total            = $order->get_total(); // order total                $order_currency         = $order->get_currency(); // order currency                $order_payment_method   = $order->get_payment_method(); // order payment method                $order_shipping_country = $order->get_shipping_country(); // order shipping country                $order_billing_country  = $order->get_billing_country(); // order billing country                $order_status           = $order->get_status(); // order status                ?>                <script type="text/javascript">                    jQuery(document).ready(function( $ ){                        console.log('PURCHACE EVENT');                        /* Track conversion on facebook Pixel */                        fbq('track', 'Purchase',                        {                            value: <?php echo $order_total ?>,                            currency: "<?php echo $order_currency ?>"                        });                                            /* Track conversion on Google Ads */                        gtag('event', 'conversion',                         {                             'send_to': 'AW-693771414/0MhwCMa9rLYBEJa56MoC',                             'value': <?php echo $order_total ?>,                             'currency': "<?php echo $order_currency ?>",                             'transaction_id': "<?php echo $order_id ?>"                        });                    });                </script>                <?php                // Flag the order (with custom meta data) to avoid pixel analytics conversion track script run multiple times.                update_post_meta( $order_id, '_pixel_tracking', true );              }        }    }}

Code goes in functions.php file of the active child theme (or active theme). It should works.