shipmentdocument.php

См. документацию.

<?php
 
namespace Bitrix\Sale\Exchange\OneC\SubordinateSale;
 
 
class ShipmentDocument extends \Bitrix\Sale\Exchange\OneC\ShipmentDocument
{
    static protected function unitFieldsInfo(&$info)
    {
        $info['ITEMS']['FIELDS']['BASE_UNIT'] = array(
            'TYPE' => 'string'
        );
    }
}