Yuck.
Just killed Vandacia and my quest tells me to "listen to Mehrunes Dagon", after which Dagon proceeds to say literally nothing. Even in chat (where I have a dedicated window for NPC dialogue in case I mishear thiings) there is no dialogue I can read.
After the weather changes and he is supposedly "banished", his model remains on screen, reminding me that I'm playing a video game whose software just bugged.
Talk about a way to ruin the climax of an entire expansion. Wow.
https://imgur.com/a/DThzpbY