After I upgraded a Magento 2.2.6 to version 2.2.8, I can not enter the Cache Management and All Users pages anymore. If I click the link in the menu I will be redirected to the dashboard page. Other pages like the Content Pages page or Products page have no problems.
Even if I place die('test') in the execute method of the controller of the page
vendor/magento/module-backend/Controller/Adminhtml/Cache/Index.php it redirects to the dashboard. So it should go wrong before it hits this point in the code. But I don't know where to start debugging from there.