Final Boss Bug?

[Gravton83]

I think there is a bug unlocking the final boss.

When I went to save the father, it showed me the door and I unlocked it. Then it put me back in the town. The NPC with the quest marker tells me I'm ready to go to the deepest part and says all my friends are waiting for me. I have run multiple standard runs with each character and no boss fight. I have unlocked/built all the buildings. The only research to do is for a shuriken.

Is this a bug?