Test to see the error in quiz activity page Create a S size of course with the generator [Site administration ► Development ► Make test course] . This will generate 10 assignments and 100 students. Go to the newly generated course. Create a quiz activity. Go to the gradebook. Create a new grade item (select "Setup > Gradebook setup" from the gradebook navigation menu, then click "Add grade item") named 'Test calculation item'. Edit calculation for the newly created grade item by clicking "Edit" > "Edit calculation". Add some id numbers to the assignments and quiz, like "assignment01" or "quiz01" Create a simple calculation such as "=[ [assignment01] ] + [ [assignment02] ] + [ [quiz01] ]". Delete one of the assignments that was part of the calculation. Complete deletion by cron if it's in progress. Go to quiz activity page. Confirm 'Probably circular reference or broken calculation formula (Item name: Test calculation item)' Reload the same page. Confirm there is no error shown in the page. Return to the "Gradebook setup" in the gradebook Edit the calculation for "Test calculation item" and remove the broken ID (looks like ##gid01##) so it reads like "=[ [assignment01] ] + [ [quiz01] ]" Delete the remaining assignment that is used in the calculation Complete deletion by cron Log out and log in as a student Visit the quiz Confirm that they do not see the error message.