After planting the fusion charge on the reactor, I am transported to the beginning area of the Institute, along with Elder Maxon. Ingram and the Synth Shaun are there. The quest updates stating that I need to speak with Shaun, but when I approach him to talk, nothing happens. Clicking the action button does nothing, acting as if the AI is disabled. I can talk to Ingram but she won't transport you until you talk to Shaun. I cannot fast travel, and I have tried reloading from the reactor room, restarting the game, etc, with the same result. So I am stuck there with no way out.

Good thing I saved right before beginning Ad Victorium....