There is no way to change the identifier (rename) the object. Provisioner preserves the _name property for this purpose. If this property has a value then it gets the system object via the _id value and OpenIDM updates it to the _name value and change the target object. After modification it reset the _id value on the target object but no code cares to check the _id change.
The link was saved before the update so the link object is broken now because the target object has a new identifier value. Also see the
OPENIDM-469 bug which is related to the _id update.