I had a problem with the language menu generation -> wrong link value for default language [TYPO3 9]

[Dominik-Sch]

[TYPO3 - 9.5.15]
[PHP 7.2.34]

The link value of the default language had the same value of the current language in the language menu.

20 = TYPO3\CMS\Frontend\DataProcessing\LanguageMenuProcessor
20 {
     languages = auto
     as = languageNavigation
}

Example:

domain.de/

language menu {
    de = "/"
    en = "/en/"
    es = "/es/"
}

---

domain.de/en/

language menu {
    de = "/en/"
    en = "/en/"
    es = "/es/"
}

---

domain.de/es/

language menu {
    de = "/es/"
    en = "/en/"
    es = "/es/"
}

I added two lines of code to fix my problem.
https://github.com/studiomitte/urlguard2/blob/master/Classes/Xclass/ContentObjectRenderer9Xclassed.php

if ($pageArguments instanceof PageArguments) {
    $LParam = $newQueryArray['L']; // save L parameter
    $newQueryArray = array_intersect($pageArguments->getRouteArguments(), $newQueryArray);
    $newQueryArray['L'] = $LParam; // add L parameter to $newQueryArray
}

I'm not 100% sure if this is a bug, or I have a configuration error on my side.