First, thank you for the very prompt reply. I'm sorry that I'm taking so long to reply. I truly didn't notice it because it wasn't emailed to me ... I think I need to adjust my profile.
The behavior occurs even after the very first test (confirmed by created a new user account). I've confirmed that it happens for various user IDs (my own, a fake one, a real student one). I've checked with 'cap test time' both on and off. What I did notice recently is that after I do the quiz, it doesn't immediately appear in the list of take quizzes. I did click "grade test".
Thank you as always for your help!