In the Grading view on Moodle 2.3.3, if you click on the the green tickbox for the first user that appears in the list of students, it comes up with an error page

It only seems to happen to the first user in the list whether they have submitted a file ready to be graded or there is no submission on each page of the grading view

If you click the green tickbox of the student below the first one it comes up with the first student's grading page
As you go down the list of subsequent students it opens the previous student's grading page

For screenshots, see the follwoing forum post

https://moodle.org/mod/forum/discuss.php?d=215723