Update cyclic CDF parameters in callback

I have a cell with several CDF parameters, where some of the cyclic fields have varying options (depending on other CDF parameters). I'm updating them within callbacks, which currently does not really work. I'm changing the choices based on a few cases, but I get a warning (*WARNING* Form 'schObjPropForm', field 'serialnum': Bad value "none" Cyclic value must be one in the list of choices.) and the pcell is not updated (I'm changing the symbol based on these parameters).

Here is the callback:

procedure(msclab_cable_callback(what)
    let(
        (
            (cablelength (car (setof param cdfgData~>parameters param~>name == "cablelength")))
            (connector (car (setof param cdfgData~>parameters param~>name == "connector")))
            (partnum (car (setof param cdfgData~>parameters param~>name == "partnum")))
        )
        partnum->choices = case(connector->value
            ("foo" list("123456" "98765"))
            ("bar" list("none"))
        )
        partnum->value = case(connector->value
             ("foo"  "123456")
             ("bar" "none")
        )
    )
)

In the pcell I of course define the CDF parameters, the CDF callback is also properly triggered.

What am I doing wrong?

Kind regards,

Patrick