Grails + Mongo: GORM mysteriously thinks a object referenced by an embedded field has a changed propery

Question

I have a domain class called Form which has an embedded field called union of type Organization which is embedded. Organization has the field createdByUser. User has a field organization of type Organization added by AST transformation.

So, whenever i try to save a Form object, it tries to change the user reference by createdByUser to an organization id of 1 for mysterious reasons.