In courses with more than 10000 students, when trying to grade student assignment submission in the mod_assign grading table, selecting 'Grade' links to wrong student on grading page.

Steps to reproduce:
1) Course with > 10000 students enrolled.
2) Create assignment with file submissions and marking guide grading method. Also enable Hide grader identity from students, Use marking workflow, Use marking allocation and ensure separate groups is being used.
3) As teacher/admin, enter into assignment grading table. Ensure no filters are set.
4) Select last page.
5) Select 'Grade' for any student.
 
6) Grader directed to wrong student in grading page. Specifically directed to first student in list (1 of 10000).