Bloomberg Sales & Analytic interview questions

I did 4 interviews over a period of approximately 2 months; a phone interview, a 1:1 interview and a couple of 2:1 interviews with more senior people. The phone interview was a conference call between me and 2 interviewers, and lasted for 30 mins. Quite long actually, and included a lot of questions to show my interest in the company, along with some finance questions. I passed this one along with 2 other interviews. The other interviews included finance, sales, customer service and personal questions along with questions about the company and its products. Not quite easy. I wasn't successful in my last (4th) interview. Although the interview as a whole wasn't so bad, the manager who interviewed me didn't quite like my answer to one of the questions. He kept on asking me the same question all over again which stressed me out. I am not sure if it's fair to be rejected after getting this far and for messing up in one question only. My advice is: expect the unexpected and don't put all your eggs in one basket.