Issue #22764: Quest "Blood Bank" breaks stage in main quest "Tour of Duty"
The following bug occurs on the Prydwen, centering on scribe Neriah (http://fallout.wikia.com/wiki/Neriah).
Scribe Neriah gives a repeating cash-for-item quest called Blood Bank (http://fallout.wikia.com/wiki/Blood_Bank).
However, Neriah is also part of a stage in the main quest "Tour of Duty", wherein the player gets to "take a tour" of the Prydwen and talk to all the important people on-board (http://fallout.wikia.com/wiki/Tour_of_Duty).
For whatever reason, upon first reaching the Prydwen, I had decided to talk to everyone on my own (without realizing that I would soon be asked to do so anyway by the quest "Tour of Duty". This included speaking to scribe Neriah, who then gave me the quest "Blood Bank". The quest "Blood Bank" never ends, and from the moment of accepting said quest, Neriah's dialog changes to deal exclusively with the viable blood samples (http://fallout.wikia.com/wiki/Viable_blood_sample). Her previous dialogue tree is made unavailable to the player from the moment of accepting "Blood Bank".
However, the quest "Tour of Duty" depends at one stage on her having (i.e. displaying to the player) the same 'regular' dialogue tree she had BEFORE I accepted "Blood Bank" from her. As such, it is now impossible for me to complete "Tour of Duty" (due to her ONLY being able to discuss viable blood samples), thus BREAKING progression of the main quest.
"Tour of Duty" obviously expects the player to be able to have certain dialogue with her in order to proceed. Well, all she's able to do now is perpetually discuss viable blood samples - and ''only'' that. It would appear "Blood Bank" gets 'dialogue priority' for Neriah, despite the fact that a part of the main quest totally expects her to be able to discuss other topics during (atleast) one critical stage.
I am running the latest official patch, NOT running any of the DLC, and running the Fallout 4 Unofficial Patch v1.0.6a. I've not screwed up any of the basics (i.e., confusing which versions of things I am running or anything like that).
This fatal bug should be easy to reproduce. Just start a new game, coc to the Prydwen, talk normally to Neriah and activate Blood Bank via dialogue, coc away and rest, then use setstage to the normal lead-up to "Tour of Duty", coc to the Prydwen, and play normally for a few minutes to see what happens when a prior activated "Blood Bank" interacts with a later activated "Tour of Duty".
I hope this was informative enough, and I hope to see this investigated, as it's rare to see the main quest genuinely break via a "prematurely activated" repeating side quest. "Tour of Duty" obviously did not expect that the player had spoken to Neriah before, and "Blood Bank" obviously does not expect that the player will have ANY need for any other future dialoge with Neriah after accepting "Blood Bank".