The questions chosen with each attempt of a quiz are independent of previous attempts; Canvas does not consider which questions you've already seen when picking questions. I've written about this in other places where people were upset that some questions in their banks were never getting delivered while others seemed to be oft-repeated.
I haven't used them, but I wonder if MasteryPaths might be able to do something here. Depending on the score on the first quiz, they go down a path that gives them a different quiz with completely different questions. I don't know how complicated MasteryPaths can be, but I suspect it will not completely solve the issue since the goal is to have the students to be able to exit at any point once a satisfactory score is met. That means that you might be able to get one additional quiz, but then the students could repeat the bad behavior with the second quiz.
One of the features that New Quizzes has is to require a minimum time between attempts. This would allow forcing students to wait 1 hour (pick a time) between attempts and possibly cut down on the pure guessing. See this lesson in the Canvas Instructor Guide https://community.canvaslms.com/docs/DOC-15053-4152780618 for more information. That won't cut down on sharing answers, but that's where the large pool of questions helps.
This discussion post is outdated and has been archived. Please use the Community question forums and official documentation for the most current and accurate information.