Can't seem to fail a quiz...

Hmm, I see that Q3 is worth only 1 point while the others are worth 25. But, your problem is beyond just that (frex, I get the certificate even when I get 25 out of 76 correct). I am relatively inexperienced when it comes to quiz items; I prefer building the questions from scratch instead. But, while I could define the correct answers for Q1, Q2, and Q4, I cannot find where the correct answer for Q3 is defined. Again, being not too familiar with quizzes, I wonder if that is a flaw with the fill-in-the-blank question.

It wouldn't be too hard for you to re-create this quiz using only form elements. Just make sure you place each question in its own form so you don't have any conflict between multiple choice questions. Then, when the learner clicks on Submit, you run an action to go to Certificate if all of the following are true: Question_0001 = False, Question_0002 = Rocks, Question_0003 = x, Question_0004 = Rock. On Else, you go to the bummer page.

It may be more work to create quizzes from scratch, but I've never really been satisfied with the default quizzes that come with Lectora. And this may be one reason why.