The main problem with asking the same question over and over again in interviews is that you are implicitly comparing the current candidate to previous candidat

The main problem with asking the same question over and over again in interviews is that you are implicitly comparing the current candidate to previous candidates, which isn't fair. If someone genuinely has never seen a problem before, and then figures it out in 45 mins, this person may look worse than someone who memorized the answer, and solves it in 10 mins. The best solution is to give a previously unknown question to both the interviewee and the interviewer, and have them work out the solution together. It doesn't have to be a coding question, but the interviewer should be good enough to assess whether or not the person they are interviewing is good, not from how quickly they spit out an answer, but through how they work to get the answer.