by Davo Smith.
Just a quick thought - there is a setting to limit the number of submissions allowed (immediately under the setting for allowing resubmissions in the first place). If you set that to 2, then this should avoid the issue for any future assignments.
I was sure my original implementation of this feature included an option to undo the resubmission, but looking again at it now, it doesn't appear to be there. It must have been removed when the code was refactored before becoming part of Moodle core.