I found this JIRA which sounds similar to both of our problems, but I'm haven't tried it yet because our particular problem was intermittent and I didn't have a way to reproduce it. so I wouldn't have a way to test if it solved our problem. But maybe it'll work for you?
We are using Sakai 11.2 and we notice that error occurs on multiple choice question with multiple correct, multiple selection where ALL the responses were correct (faculty thought this is supposed to be a trick question, sort of)
Student's answers are checked correctly (marked as Green), but the score is not correct.
5) Choose the answer configuration: "Multiple Correct, Multiple Selection", "All or Nothing", and point deduced for incorrect answer: 0.75
6) add correct answers A thru G (mark all the responses as correct).
7) Randomize Answers: Yes and save the question
As a student:
take an exam and mark all the options as correct.
This student has checked every response as she should and all her answers are marked as Green (indicate the correct answers), but she is getting the -0.75 points for getting the exam wrong rather than a 1.5 which she should get for the exam.
In order to confirm this behavior, I create a new exam with A thru F correct answers (note: previously all answers are correct and now in this question there is one incorrect answer). This new exam works as expected.
Please let me know where I can find the JIRA or fix for this issue.