tamer restricted knowledge.

I did the quest with two characters, first the left side then the right side, the first time I did it, I had the [Crossroad] General of the Land of the High Clouds quest selected, and I also completed the [Bulgasal] Two Steps Forward quest, but the knowledge didn't received
From the knowledge category Morning Light - Hwanghae Tales I, this is the only knowledge that has not been obtained.
How can І not get knowledge from the main chain? Maybe it's a bug, I don't know

Чтобы получить знание проходите тамером и выбираете вариант тот что слева, вы должны попасть на остров Хеммо, после убийства пульгасари старик даст знание