Prevents WooCommerce from auto-completing subscription renewal orders that have $0 product value but include shipping costs. Forces these orders to remain in processing until manually completed.

prevent-autocomplete-renewal-orders-with-shipping.php

/**
 * Prevent WooCommerce from auto-completing orders with $0 product total but shipping costs.
 *
 * @param bool     $is_virtual Whether the order contains only virtual products.
 * @param WC_Order $order      The order object.
 * @return bool
 */
function a8c_prevent_zero_value_order_completion( $is_virtual, $order ) {
	// Only modify behavior for subscription renewal orders
	if ( function_exists( 'wcs_order_contains_renewal' ) && wcs_order_contains_renewal( $order ) ) {
		// Check if order has shipping costs
		if ( $order->get_shipping_total() > 0 ) {
			// Force non-virtual status to prevent auto-completion
			return false;
		}
	}
	
	return $is_virtual;
}
add_filter( 'woocommerce_order_is_download_only', 'a8c_prevent_zero_value_order_completion', 10, 2 );