Simon,
To find out the version of Moodle, you can go to any page in your site and look for the "Moodle Docs on this page" at the bottom and the link will take you to Moodle.org. The version will be in the URL... such as https://docs.moodle.org/28/en/ would be version 2.8.
The reason I asked for the number of questions is that when Moodle quiz goes to a new page, it saves the answers even though they haven't been submitted. Until we got instructors to put 5-10 questions on a page instead of 25-75 plus on a page, we sometimes had students who lost their work when they had internet problems.
In 2.5 there are 3 settings for the timing on the quiz. See documentation here. Teachers can set the quiz up so that the attempt has to be submitted before time expires or it's not counted, open attempts are submitted automatically when time is up or there is a grace period for submitting but no more questions can be answered. We recommended that instructors use the grace period to help prevent the problem and give the extra time for submission. Moodle doesn't know why the submission is late, it just knows that it is. If the server is a little slow at the time because a lot of students are submitting at once, the server may count the quiz as late unless there is a grace period selected.
I hope that helps.
