We're running into an intermittent problem where teachers enter grades for an "advanced uploading type of files" assignment. The teacher enters the grades directly in the assignment tool and later when she wants to update a grade finds that the grades have been overridden in the gradebook. She's the only teacher so there's no mischief there and she's not entering grades or comments directly in the gradebook. Of course, she can go into the gradebook to uncheck the override box but it's a mystery as to why the assignment for entered grades must now be overridden in the gradebook.
So the question is does anyone know of a sequence that could be causing this problem? I didn't see a bug in the Moodle Tracker about this. Also, there are no locks on the assignment so there don't appear to be any assignment parameter settings that may be affecting it.
We're using Moodle 1.9.2 with Postgres on an Apache/linux server.
Does the teacher use by any chance the quick grading and the popup grading form simultaneously? If the quick grading is enabled and the teacher uses the grade link to update a grade and/or a comment and then returns to main list and save the quick grading without reloading the page, the grade and comment she entered in the popup form are not preserved and are not passed to the gradebook. 
Yes she does use the quick grading and popup form. The problem is that sometime later she can't update the grade from within the assignment tool. It's like the grade was entered in the gradebook instead. So, she then has to uncheck the override box, remove the grade, and save her changes in the gradebook before she can go back to the assignment tool to update the grade.
I can't reproduce it. Can you pinpoint how it happens?
We had an instructor report a similar issue. I'm wondering if it has something to do with copying and pasting from Word - all of the submissions that were overridden in the gradebook had a lot of extraneous markup leftover from Word.