Quizzes freezing

[Amy6102]

The last quiz (test) I gave had student's quiz page suddenly not able to move to the next question. I was hoping that it was just a temporary thing, however, it is doing it again today. It is very random and does not happen to every student. For some, they can shut down their Chromebooks and it will start them up right where it froze. For others, they lose not only the question they just finished, but several before that, as well.