Some props are not assigned on save_post_shop_order

I am trying to send order data to a backend in a plugin with the hook ‘save_post_shop_order’. But some props like ‘customer_id’ seem like not assigned/saved yet. This happens when I try to create an order manually in admin panel. I also tried ‘woocommerce_after_order_object_save’ hook and that is not suitable for my need. Is there another hook available or is this some kind of bug in woocommerce?