First of all, thanks a ton!
However, I'm not sure about that bug. Many people (including both of us multiple times) have beaten this trial without any issues. The way the duel works is that to advance you need 5 correct answers in a row. So maybe you made a mistake on a different question, and not the one you are thinking about?
The correct answers for duel 2 in chapter 4 are as follows:
Round 1: 2,1,1,2,1
Round 2: 2,2,1,1,2