Custom fields on invoice stopped working in woocommerce 2.1?

There seems to be a problem using woocommerce 2.1.5 and woocommerce delivery notes 2.0.5 with custom field values not showing any more. I’ve done some research and

This post: https://wordpress.org/support/topic/custom-order-fields-changed-in-woocommerce-21

..seems to be of some help.

I think the problem lies in the order_custom_fields that needs to be changed into meta_key_name.

I guess this needs to be done in the class-wcdn-print.php file in the get_order_field function? I’ve tried this, but I didn’t seem to get this to work. Any help?

https://wordpress.org/plugins/woocommerce-delivery-notes/