Error Page is shown in wrong language

I have spotted a really weird behaviour with my error pages.

If I browse my site in english and enter a not existing url, I get redirected correctly to the error page. Unfortunately all the content (and navigation and everything else) there is always shown in the default language german. However the URL path is still with /en/.

Any ideas on where I need to start debugging?

I tried a few things out and it seems that everything is set up as it should be.
There is an /error folder with the content files for each language. If i hit an error, i get forwarded to the correct error site. However, everything still remains in german, and the language switcher changes to german as well. Is this potentially a bug in Kirby with multilanguage sites?

Please post your language configuration. Also, are you using any routes? Language detection? Plugins?

I’m not using any routes, language detection is on. Plugins I’m using are kirby3-xmlsitemap and uniform.
Language configurations:
DE
‘code’ => ‘de’,
‘default’ => true,
‘locale’ => ‘de_CH’,
‘name’ => ‘Deutsch’,
‘url’ => ‘/de’,
‘translations’ => […]

EN
‘code’ => ‘en’,
‘locale’ => ‘en_US’,
‘name’ => ‘English’,
‘url’ => ‘/en’,
‘translations’ => […]

@texnixe do you have any other ideas here?

No, I haven’t tested this myself yet, but found this issue: https://github.com/getkirby/kirby/issues/2609

I just tested this with a fresh Starterkit and can reproduce the issue.