TYPO3 Core

I have defined a field "Media" in the TCA (removed the overrideChildTca part to make it more readable).

        'media' => [
            'exclude' => true,
            'label' => 'Media',
            'l10n_mode' => 'exclude',
            'l10n_display' => 'defaultAsReadonly',
            'config' => ExtensionManagementUtility::getFileFieldTCAConfig(
                'media',
                [
                    'maxitems' => 20,
                    'behaviour' => [
                        'allowLanguageSynchronization' => true,
                    ],
                ],
                $GLOBALS['TYPO3_CONF_VARS']['GFX']['imagefile_ext']
            ),
        ],

If I add files in the default language to this field, everything works as expected and I also see the files in the translations.

If I then change the "Translation behavior" from "Value of default language" to "Custom value" in a translation in the backend, however, nothing changes in the form. Even saving the record does not change anything.

I would expect to be able to override the value with the setting. With other fields (e.g. nav_hide in pages) the form already changes when the setting is changed (without having to save).

The browser console does not show any errors in Chrome.
The limit of "maxItems" has not been reached!