by Guido Roessling.
I have figured out some time ago what the issue is - sadly, it remains an issue even in Moodle 2.5, so I wonder if this is "intentional behaviour".
Quite simply, the decision on whether to show the submit for grading button ignores whether the submission is still open. By adding a ... && $this->submissions_open() at the right place, the problem goes away - until the next update...
