Problem with payment plugin

It’s standard payment plugin which get order like this

/**
			 * get_borica_order function.
			 *
			 * @param  string $custom
			 * @param  string $invoice
			 * @return WC_Order object
			 */
			 public function get_borica_order( $order_id ) {
					
					$order = wc_get_order( $order_id );
			
					if ( ! isset( $order->id ) ) {
						global $wpdb;

					    // Faster than get_posts()
					    $order_id = $wpdb->get_var( $wpdb->prepare( "SELECT post_id FROM {$wpdb->prefix}postmeta WHERE meta_key = '_order_number' AND meta_value = %s", (int)$order_id ) );
		
					    $order 		= wc_get_order( $order_id );
					}
					return $order;
			 }

And later I’m using with object from above.
$order->update_status( 'on-hold', "Payment NOT confirmed")

Will check which function should be used

Yes I can confirm that if I disable Custom Order number plugin error is disappearing.
The code is executed in external file like this

<?php

if (!function_exists('add_action')){
		require_once("../../../wp-load.php");
}

if(!session_id()) {
        session_start();
}

$borica = new WC_Gateway_BORICA;

$order = $borica->get_borica_order( 111 );