We have 2 languages running on a K2 based website. In the K2 category blog, which is set to language: all, there are K2 Items set to German and others are set to English. The K2 items are displayed correctly in the category overview.
Since the K2 2.10 update, when accessing a K2 item via the category overview in the German version of the site, the result is a 404 error - category not found. In the English version of the same category, the k2 items still work normally.

Here are the links:
DE: Category Overview German: www.spotteron.net/de/blog-und-neuigkeiten
DE: Accessing first K2 Item in Overview: www.spotteron.net/de/blog-and-news/citizen-science-award-2019-event-gala-wien

EN: Category overview in English: www.spotteron.net/blog-and-news
EN: Accessing a K2 item in English works normally: www.spotteron.net/blog-and-news/desktop-vs-mobile-what-s-best-for-citizen-science-projects

Here is the Joomla Debug Output of a german K2 item with the 404 Error:

404 **Kategorie nicht gefunden**
Call stack
# Function Location
1 () JROOT/libraries/legacy/error/error.php:200
2 JError::raise() JROOT/libraries/legacy/error/error.php:277
3 JError::raiseError() JROOT/libraries/src/MVC/View/CategoryView.php:133
4 Joomla\CMS\MVC\View\CategoryView->commonCategoryDisplay() JROOT/components/com_content/views/category/view.html.php:75
5 ContentViewCategory->display() JROOT/libraries/src/Cache/Controller/ViewController.php:102
6 Joomla\CMS\Cache\Controller\ViewController->get() JROOT/libraries/src/MVC/Controller/BaseController.php:663
7 Joomla\CMS\MVC\Controller\BaseController->display() JROOT/components/com_content/controller.php:118
8 ContentController->display() JROOT/libraries/src/MVC/Controller/BaseController.php:710
9 Joomla\CMS\MVC\Controller\BaseController->execute() JROOT/components/com_content/content.php:43
10 require_once() JROOT/libraries/src/Component/ComponentHelper.php:402
11 Joomla\CMS\Component\ComponentHelper::executeComponent() JROOT/libraries/src/Component/ComponentHelper.php:377
12 Joomla\CMS\Component\ComponentHelper::renderComponent() JROOT/libraries/src/Application/SiteApplication.php:194
13 Joomla\CMS\Application\SiteApplication->dispatch() JROOT/libraries/src/Application/SiteApplication.php:233
14 Joomla\CMS\Application\SiteApplication->doExecute() JROOT/libraries/src/Application/CMSApplication.php:196
15 Joomla\CMS\Application\CMSApplication->execute() JROOT/index.php:49

Any fast advise is welcome, since the whole german Blog is not working anymore due to this error,
Thank you and best regards,
Jonathan

Thank you very much!