DELVE Unspoeakable shrine bug(?)

Hi.

Ive encountered an abyssal depth in a delve, named Unspeakable shrine, and when i enter there is 3 guys inside green shields doing something to a shrine in the middle, but nothing happens.

Cant kill anything, cant interact with anything. How do i start this encounter?

EDIT: I think i found the reason, an Obelisk of binding isnt killable, therefor the encounter cannot start