I don’t think it was your Cloud of Daggers. My party all failed the perception check to find the real chest, so I thought I’d have a go casting Light on a fake one, and that made the other mimics appear and triggered everyone to appear with speech bubbles over their heads as though in dialogue, locked in that state. I assume there’s going to be something said at that point in the full release.
As you say, pressing space bar will move things along, as I think it does some other stuck dialogue related issues elsewhere.
