TYPO3 Core

I'm migrating an TYPO3 project from version 8.7 to 9.5. The project has a single page tree and three different languages (german as default language, english and french).

The main menu consists of three levels and is generated by a fluid data processor:

page.10 = FLUIDTEMPLATE
page.10 {

    ....

    dataProcessing {
        10 = TYPO3\CMS\Frontend\DataProcessing\MenuProcessor
        10 {
            as = mainNavigation
            expandAll = 1
            special = directory
            special.value = [Page ID for menu root]
            levels = 3
        }

    }

}

This code works fine, only if the default language is selected in the frontend. If any other language is selected (in frontend), only entries of the first level are generated and their child objects are empty (do not exist).

The menu generation without special = directory property works fine in all frontend languages:

page.10 = FLUIDTEMPLATE
page.10 {

    ....

    dataProcessing {
        10 = TYPO3\CMS\Frontend\DataProcessing\MenuProcessor
        10 {
            as = mainNavigation
            expandAll = 1
            levels = 3
        }

    }

}

The second snipped generates all three menu levels correctly in all languages.