Gradebook

We have encountered this kind of issue recently.

One of the gradebooks became completely blank.
We figured out that it was caused by some background process which caused endless loop of memory consumption.

The instructor was attempting to delete a grade category from the course and apparently clicked the submit button twice.  Even though we were not been able to reproduce this error ourselves, the timing of the two clicks must have been just right to corrupt the category assignment for the graded items that were in the deleted category; those graded items are still associated with the id of the deleted category.

The blank page occurs because the logic goes into an endless recursion loop when the graded item is associated with a category that does not exist (or, as we think, is not associated with the same course).
The endless loop consumes all available memory and the response fails.

We believe it is the same issue as the one with the invisible assignment submissions.

Anyone encountered the same issue? Any code tips?
We do not want to change anything in the database to fix existing problems, we would rather fix the cause

tia