id was called incorrectly. Order properties should not be accessed directly

Since the last update ~2 days ago we have the following error spamming or error log:

id was called incorrectly. Order properties should not be accessed directly. Backtrace: require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'), do_action('template_redirect'), WP_Hook->do_action, WP_Hook->apply_filters, WC_AJAX::do_wc_ajax, do_action('wc_ajax_checkout'), WP_Hook->do_action, WP_Hook->apply_filters, WC_AJAX::checkout, WC_Checkout->process_checkout, WC_Checkout->process_order_payment, WooCommerce\PayPalCommerce\WcGateway\Gateway\PayPalGateway->process_payment, WooCommerce\PayPalCommerce\WcGateway\Processor\OrderProcessor->process, WooCommerce\PayPalCommerce\WcGateway\Processor\OrderProcessor->handle_new_order_status, WooCommerce\PayPalCommerce\WcGateway\Processor\OrderProcessor->handle_capture_status, WC_Order->payment_complete, WC_Order->save, WC_Order->status_transition, do_action('woocommerce_order_status_pending_to_processing'), WP_Hook->do_action, WP_Hook->apply_filters, WC_Emails::send_transactional_email, do_action_ref_array('woocommerce_order_status_pending_to_processing_notification'), WP_Hook->do_action, WP_Hook->apply_filters, WC_Email_Customer_Processing_Order->trigger, WC_Email->get_headers, apply_filters('woocommerce_email_headers'), WP_Hook->apply_filters, WCJ_Product_By_User->sendemail_to_productowner_order_place_successfully, WC_Abstract_Legacy_Order->__get, wc_doing_it_wrong. This message was added in version 3.0.