Hibernate - merge deletes parent when using @Cascade.

Issue

I have experienced some strange behaviour in hibernate I need your support with.
In general the setup looks like this:

one Formular has several Vermittler and several PersonManuell which both are cascade all-delete-orphans.

if a Personmanuell is removed from Formular and Formular is Merged, the PersonManuell entry gets deleted and everything is just fine.

if a Vermittler is removed from Formular which is then merged with the DB, the whole Formular is deleted as well which definitively is not what we wanted. Only the removed child should be deleted. also it does not matter if Formular has any other children, as soon as a Vermittler is deleted, the entire Formular gets deleted.

Hibernate-Version: 3.2.4.sp1.cp11