new quizzes autosubmit

[panjac]

Has anyone had any issues with new quizzes auto-submitting for students?  I have a teacher who assigned students a quiz (no time limit) and kids started working on it in class, then went home and opened it back up and the quiz submitted on its own while they were working on it.  I had her reopen it for the students who had the issue, but just wondering if there is something that I am missing as to why it submitted for them?