Update subordinate UDF

Hello everybody,
i am trying to update an fdu with no success.

Here are the steps I took:

1 - I draw the .prt which has the udf.
2 - I create the udf as a subordinate.
3 - I save the udf and the reference model in the working directory
4 - I create a new part and recall the udf as dependent on udf quotas and salvo.
5 - I reopen the reference model of the udf and I modify it and I also modify the fdu itself (ex: I delete a rounding feature) and save.
5 - I go back to the part and from> udf operations> update everything

After the operations described, I don't see the UDF updating.
It updates only if I manually go to replace it.
Is there an automatic way?
Why doesn't it update with the command updates everything?

ty,

Matteo.