RESOLVED: As of 12:00PM 9/28/21, the Moodle Assignment Grading feature is functioning as expected. If you are still experiencing issues, please submit a ticket to ITS.
ITS is currently investigating an issue regarding assignment grading in Moodle.
We ask that users do not attempt the assignment grading feature in Moodle for the time being. We will update the community as more information becomes available.