When completing a quiz that has a 'grade to pass' specified (http://docs.moodle.org/en/Activity_completion) it marks it as 'Completed' with a tick when the quiz has been finished, regardless of the grade the student accomplished. This happens because the 'Scores' option under the 'Review options' 'Later, while the quiz is still open' was not set. On the documentation page it states 'There is one limitation: this only works if grades are immediately visible to students'. However, when regenerating the results by editing the quiz and choosing 'Unlock Completion Options' and then click 'Save and return to course' it will then display the correct icon (when the user logs in and out as the icon is stored in the user's session), which in this case was supposed to be a cross. I am not sure which behaviour is expected, if it should be a cross or tick or neither when the score is hidden. Either way there are two separate situations happening.