Add some minor php mis coding error that can generate a warning before a redirect function call. For example: Add "$deleteme = get_string('nooooooo');" just after the line starting with: "$CFG->additionalhtmlhead" on the login/index.php page. Turn Debugging on (developer mode) and turn Display debugging on too. Login into Moodle If you are viewing Moodle using an English UI, You should be seeing the same error message, but after this issue is accepted and local language translators start translating this string token, You should be seeing the error message translation in your own language.