Non-empty answers identified as blank
Many answers are pre-graded as blank, when they are not blank. It might have to do with the size of the required answer: "(1,4)", but 90 out of 198 being graded blank is too much (some were actually blank of course, but still). (This is question 5b from am1010, midtermupdate)
This can be very dangerous as ideally we do not check if the blank answers are truly blank, thus not grading correct answers.