Altering Text Grades A-F

Has anyone else had the problem when going into Grade Types & trying to alter 'Text grades A-F' and only a few of them are visible?

I can scroll down and alter the lower grades, but when I scroll up, the page just bounces back to where it was, so I can't click on the percentages of A+ and A to change them.

Does anyone know how to fix this?

Hello,
I think I replied to this by e-mail already, but here it goes...

I've prepared a short video here , let me know if you can spot
the difference.
As an alternative method, if altering a single grade is the problem, you can erase
a specific row (swipe your finger from right to left) and add a new one instead.

Hope this helps!