One of the proctors leaked all the answers for the tasting portion of the 2018 exam (widely reputed as the hardest--by a vast margin--portion of the 3-part Master Sommelier exam) to two people.

And because the group of test-takers each year is so small and they are all in constant contact each other for study and practice, it was impossible to know how many people got the leak.

And so they just blanket disqualified everyone and made them all retake the test next year.