I have had students on slow internet connections complain that the quiz froze, and students with power outages need to resume a quiz that was interrupted. I set lockdown browser to allow them to re-enter their current attempt, and then I simply monitor for reports that students are leaving and re-entering the quiz.
With this student, I would check the quiz log. If you display one question at a time, it will tell you how much of the quiz your student saw, and how much time they took to get to that point. In new quizzes, one of the moderate options is to re-open the current attempt. I expect that it would reopen with only the remaining time of a timed quiz, based on the time listed for how long this attempt took. If that time shows that the student took the full time of a timed quiz, but the quiz log shows a shorter time, you may need to add the difference in the two times as additional time if you choose to reopen a timed attempt.
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