IdFixUp won't fix up grandChilds

Hi,
I have 3 tables, parent - child - grandchild.
Parent has an autoincrement id as a PK
Child use id and an ean-number as a PK (all wrong, compound key _and_ natural key :-))
GrandChild, which holds lines for childs uses id, ean and lineNumbers as a PK.
I create some parent entities and I see that devForce give them a negativ id.
The problem arise when I save my entities. The id in parent and child get fixed but not the one in the grand child and this lead to a constraint violation.
As a work aroud I use a "ForceIdFixUp" after the creation of the Parent entities.
Extra info: I am working on the serverside but the persistance manager originate from a smart client which called a ServerRpcPersistenceDelegate through the BOS.

Am I missing something?