[TYPO3-mvc] T3 6.2 Exception while property mapping / CONFIGURATION_CREATION_ALLOWED

[g4-lisz at tonarchiv.ch]

Hi there

I have some issue with a action controller when updating data from a
form viewhelper.

The extension worked in 4.6. Now I get this '#1297759968: Exception
while property mapping at property path "type":Creation of objects not
allowed. To enable this, you need to set the
PropertyMappingConfiguration Value "CONFIGURATION_CREATION_ALLOWED" to
TRUE' error.

"Type" is derived from the AbstractValueObject class. It's a property of
the new object "newPdfbericht" to be added, and it is selected by radio
buttons:

        <f:form enctype="multipart/form-data"
action="qualitaetsberichteUpdate" name="newPdfbericht"
object="{newPdfbericht}">
                    <f:form.upload name="file"/>
     ....
                    <f:for each="{pdfberichtTypes}" as="pdfberichtType">
                        <label>
                            <f:form.radio property="type"
value="{pdfberichtType}"/>
                            {pdfberichtType.name}
                            <br />
                        </label>
                    </f:for>
        </f:form>

$pdfberichtTypes = $this->pdfberichtTypeRepository->findAll();

The rendered HTML for the radio form field looks like this:
    <label>
        <input type="radio" value="1"
name="tx_hplusinfo_pa_qualitaetsberichte[newPdfbericht][type][__identity]">
         Struktur H+
        <br>
    <label>
        <input type="radio" value="2"
name="tx_hplusinfo_pa_qualitaetsberichte[newPdfbericht][type][__identity]">
         eigene Struktur
        <br>
    </label>

I don't understand why the property mapper has to create a new "Type"
object...

Nevertheless, I added this intialieze function to the controller:
        /**
         * @return void
         */
        protected function initializeQualitaetsberichteUpdateAction() {
                $propertyMappingConfiguration =
$this->arguments['newPdfbericht']->getPropertyMappingConfiguration();
                $propertyMappingConfiguration->allowAllProperties()
                       
->setTypeConverterOption('TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter',
\TYPO3\CMS\Extbase\Property\TypeConverter\PersistentObjectConverter::CONFIGURATION_CREATION_ALLOWED,
TRUE);
        }

But still the same error. What I'm doing wrong? Maybe a TCA issue of
PpdfberichetType" or "PdfBericht"?

Any help would be much appreciated! I'm really stuck here...

Cheers,
Till