Bug (?): Tireless mechanic quest

Hello, not sure if this is the right place to post this, but I seem to have run into a bug on the Tireless Mechanic quest. I’ve been to the penultimate chamber of the castle, and selected the Tireless Mechanic’s option, and I have the rescued prisoner. But now, nothing. I see no option to keep the quest moving. Have I missed something, or is this a bug?

I love the game, and am excited about closing out the quest so any advice appreciated.

There is a list of notes of what you need in your ‘objectives’ tab of your gazeteer.

Specifically you need a cask of sapphires, and element of dawn, and 40 stygian ivory taken to kingeaters castle.