My first quiz with my class was almost disaster. The attempts of 24 of 40 students were not saved, and most disturbingly there was no error message. In the log I can see that attempts of the students so I am sure everybody submitted the quiz.
I suppose the problem was with the random questions because at those people whose attempt was not saved in the log at random question there was only text "random set", but at the other people the randomly selected question appeared.
Istvan