Working
CONSTRAINT `FK_users_orders` FOREIGN KEY (`cus_id`, `ord_id`) REFERENCES `orders` (`cus_id`, `ord_id`)
is always formed like
CONSTRAINT `FK_users_orders` FOREIGN KEY (`cus_id`, `ord_id`) REFERENCES `orders` (`ord_id`, `cus_id`)
(reversed order because of the sequence fields appear in the corresponding tables - e.g. order is the field "number")
... which is incorrect I believe.
Regards.
smooker.