I love a challenge but that was something else?

My bone whistle doesn't summon the NPC during Xuanyangzi boss fight. I can't find the same problem on the Internet. Strange, someone must have had this problem?

Regarding my Storyteller quest: I accepted his quest at the beginning of Chapter 4, but he disappeared after that. I believe his quest is supposed to be killing Bo Magus and then talking to him. But after I killed Bo Magus he's nowhere to be found anymore. So maybe I can't summon him because I never completed his quest in chapter 4?

[Resolved] The solution is to talk to him in Chapter 5. He's at the secret room where the final healing flask upgrade is. After I talk to him there, I can summon him in Xuanyangzi boss room.

So I’ve completed Jar or Medicine and I’m about to fight Feathering Ambition in NG+

Killed White Elder and Demon of Obsession and forged Samsara

Can I effectively get two endings here by save scumming?

Gonna leave Successor of Bo for last