Usually the question was removed if a lot of people were challenging it. This was when 3/5 questions would get you credit for the entire module though. On the new tests you dispute it while taking the test, you just hit the dispute button or whatever (it’s been awhile, I don’t remember exactly how it worked), and type up your comments on the question.
How would you know if you got one wrong on the new tests? It’s pass/fail so I’m not sure one question would that you don’t even know if you got wrong or right would make a difference?