Several faculty reported extreme slowness when entering grades in Moodle. After reporting the issue to ethink, our hosting service, they replied with this information.
“We have seen issues with the grader report lagging when using chrome when editing is turned on. I have asked our admins to apply the fix for this. In the meantime we have seen the grader report page is much smoother in Firefox. It also seems to work well if you go to the single view page instead of the whole view."