You'll need a course with at least one student and at least two gradeable activities. Setup Create a new calculated grade item. Set it to be equal to the sum of two other grade items ie =[ [itemA] ]+[ [itemB] ] Go to the user report (in the gradebook) and check that you can select individual students from the drop down. Export the course grades and check that you can export the grades without error. Make sure that both your activities and your users have an ID number set ( http://docs.moodle.org/23/en/Grade_export#XML_file_export ). Check its broken Delete one of the activities that is relied upon by the calculated grade item. Now, the user report should give you an error. The error message should tell you that there is a circular reference or broken calculation formula. Similarly grade export should give you an error. Student still works Log in as a student and check that you can access the user report and that you don't see the exception message. Within the user report the calc grade item will report an error but the report itself should load. Check its fixable Log back in as teacher/admin, go to the categories and items screen and remove the reference to the deleted grade item by editing the calculation. The missing grade item name in the calculation will have been replaced with a token. Check that the user report now loads for the teacher/admin.