With the Assignment module (Offline task) there are 3 Optional settings at the bottom of the 'View xx submitted assignments", i.e. the page where the teacher can see the list of students in order to grade them.

The first of these three optiona is a drop-down memu: Show: which contains 3-choices: 'All / Submitted / Require grading'

If teachers select "Require grading", they get this error message:

"No users were found with permissions to submit this assignment"

At this point, if a teacher clicks on the browser back button, and returns to the previous screen, he/she will see the list of all the students as before. HOWEVER, if he/she does something else, e.g. returns to the course page, he will be unable to see the list of students the next time she accesses the assignment since the optional setting for 'Show' will be locked in to "Require grading" resulting in the above error message.

Note: clicking on the other 2 choices (All or Submitted) in the Show menu works as expected.