[TYPO3-mvc] extbase update a root object updates foreign child objects

[Matthias Schubert]

Hello,

I have an issue concerning extbase and the update() method.

I got an existing root object which already was in the repository with 
no child objects. What I do is adding many child objects to the 
transient root object und persist it to the repository with 
update($root).

What now happens is, that older child objects from other root objects 
are updated and so deleted for the other root. Why is this happening? 
Is there a failure in the model? How can I avoid this?

I will be very thankfull for any suggenstions.

Regards,

Matthias