Not working when it is checked doesn't really make sense, as it would set a more permanent cookie would would help workaround issues. Not working when it's not checked would be more expected, from a bug report point of view.
When I tried it for the first time I checked the box and used the correct username and password it forwards me again to the login form. The same when I used a false password. And I tried it several times with the checked box and the correct password, always it forwards me again to the login form.
And when I tried it an hour ago it works fine, without problems when I checked the box.