by ben reynolds.
Stabbing in the dark here. You use "submit for grading," and everything has been submitted. Only the teacher can "revert to draft."
And another shot in the dark. If a teacher uses (Mary Cooch, help!) the grade next or something function (we don't use this at my institution), the whole assignment is locked up, and nobody can grade anything more. The most dangerous way to grade is through the gradebook. The safest way, IMO, is via the actual assignment.