Student assessment pending after being graded

HI.
If a student chooses to go back and review previous materiel and previous answers that have been already graded by an instructor in a unit, and then saves and exits that unit, then all graded answers turn into pending status as though they haven't been graded, even though already graded before.

this causes the closing of units that come after, because know the unit that has pending answers from the student is not complete.

Unfortunately this is causing a lot of headaches to a lot of students.