I had a situation when I have to override all the grades of a student in a certain quiz, since the quiz is not on Moodle (our internet connection was taken down temporarily).

However, I can only override the grades of the first few students. I think it has something to do with the number of textboxes present in the grade view.

I can override up to the 30th student in one course, but only up to the 17th in another course.

Using the edit grade button on an individual student works though.

My hosting service allows a maximum of 64MB for post data, and 30sec time, but this should be sufficient IMO.

post_max_size 64M
max_execution_time 30

To recreate:
1. Open gradebook in Grader View
2. Turn Editing On
3. Choose a column, (e.g. a quiz), and override all grades from the first student up to the last.

Expected Result: All grades will be overriden.
Actual Result: Not all grades are overriden, only the first few students, maybe about 75% of the class.
If you take a look at the attachment, the orange highlight (for overriden) does not go all the way up to the last student.