I have just experienced a game breaking bug.
After the cut scene following the discovery of the first adra piller at the Engwithan dig site, the script should automatically start a dialogue with Eder.
I can see in the text/combat log the message "... taps you on the back/shoulder", but the dialogue never starts.
This prevents me from saving the game, makes all enemies puppets that won't move unless attacked first, and disable fast travel, just to name a few.
I haven't tried yet (dinner time anyways) to reload a previous save to see if it happens again, but very annoying nonetheless.