This must be tested in all supported browsers as the JS function being changed is used throughout Moodle. Create a new course with some enrolled students in it. Create a new assignment with setting 'Feedback settings > Offline grading worksheet' to Yes. Save and display the assignment. Log in as a student for that course and submit a file for the assignment. Go back to your Administrator role and click on 'View/grade all submissions'. Select 'Download grading worksheet' from the dropdown menu so you are are prompted to download a file. Click on the drop down box again and make sure you aren't specified to download this file again. Browse the Moodle site and ensure all drop down boxes are working as expected (adding blocks, navigating in grade book etc).