When the memcached session expires, SOGo redirects the browser to the cas login page. If the CAS cookie has not expired, the login is checked automatically and CAS instantaneously redirects the browser back to SOGo. The problem is that the new redirection leads to the /SOGo/ links, which then redirects to the user's preferred module. Unfortunately, this can happen too during an AJAX request or in a popup window (preferences, mail composition).

One way to solve this is to set a cookie during the initial page redirection that would enable SOGo to finalize the chain of redirections back to the intended page.