Enable single question preview for random questions. Add a Reload button in the popup window, clearly graphically indicated as being not part of the actual preview, for reloading the question, to give the user means to confirm the random question's contents actually are rerandomized between uses.

Example usability issue discovered in usability testing:
http://docs.moodle.org/en/Development:Quiz_UI_redesign/usability_testing_of_August_2008/Issues#Others