We are on Moodle 3.6.5.
I have a faculty member who has about 14 Quizzes on his site, with just a few questions in each. All was working fine, and then with Quiz #9 only 5 of the 33 student attempts are shown. For all quizzes later than that one, there are no attempts shown to the teacher. In some cases, there are 52 student attempts but the teacher is told there are no attempts to display.
I've verified that students did submit attempts by both logging in as them and by look at the quiz_attempts table in the database. Interestingly, students can see their own attempts even if the teacher cannot.
No one else is reporting this behavior.
I've checked permissions on the quiz and the site, but there is nothing squirrely there. What is super weird is that he has the same problem on both sites that he uses for each of his sections.
I'm totally stumped. Does anyone have any ideas?