How do you spawn the Gruesome Twosome in Hate?

Full group, same people every time. We all have the achievements to that point. We've tried half a dozen times, can't spawn the second name. The coffins aren't clickable. What are we missing?

You have to talk to Estir the Spiteful first and then click the coffin.

We've done that, no luck.

Worth noting couple of things;

Estir will have a long cast bar after/during talking, which you have to click the coffin in. If not seeing her cast something, and she attacks pretty quick, you dont qualify.

The coffin is in a different alcove, not the one directly behind her.