Usually you dont have to make him repeat himself. Theres no need to answer him right after his sayings. Normally you can give him a wrong answer thousands of times, and then make it the correct answer, it still should work.
I got this quest, but didn't get the item he was supposed to give me (the clue). Maybe I should have clicked on the "give" button to get this item? Anyway, I can't make him restart his speech, or restart / discard this quest, so I'm stuck.