I assume you mean you submitted a bug report for the problem. Thanks.
As for "Is there no way for me as the instructor to override the system's grading of the problem" what you can do is to mark that problem "correct" for the student (or give the student partial credit which in this case you don't want to do). Click on "Hmwk Sets Editor" and for the assignment in question click the numbers (e.g. 34/34) under "Edit Assigned Users", then " Edit data for ..." and for the problem in question, set the status to one. Status is not a great work but status is a number between 0 and 1 representing the part of a problem a student has gotten correct. The "status" is multiplied by the number of point a problem is worth to get the students score for that problem. Finally click "Save Changes".
If it truly a bad problem (this one sounds like one) you can under "Edit Problems" click on the number and then for the problem in quest check "Mark Correct". This will mark the problem correct for all students.