Reported this in-game and haven't gotten a response.
I was disconnected 3/3 times after killing Balthazar in "To Kill A God". Watched the post-fight cinematic, then immediately get the "game client lost its connection to the server" pop up.
Grasping at straws, I hid my outfit, Brand's Wolfblood, and skipped the cinematic and was finally able to progress. Don't know unfortunately if it was skipping or the outfit that changed things, but one of those two appears to have some issues with this encounter.