So, over a half of the NPCs (I'd say >80%) have no greeting, the dialogue goes straight into player asking questions / saying goodbyes. This causes an issue where most of the quest topics don't appear at all, most likely because it skips the NPC greeting and the player's answer to it that would normally trigger the quest. There is also the strange issue with random, unimportant NPCs (wastelanders, NCR troops, gamblers, citizens...) starting a dialogue even though they normally just speak some generic, short phrases ingame when interacted with. The only choice that pops up in their dialogues is "Goodbye."
Now, to the main issue at hand.
One example:
The player gets inside the Arlington Library, where the BoS scribe Yearling starts a conversation right when the player steps inside the building. In vanilla (and in normal circumstances) she would inquire about the player's reason to be there, which would eventually lead into the option to bring Pre-War Books to her. Instead, the game skips the whole dialogue and gives the player only the "What are you doing here?" and "Goodbye." options.
So most of the side quests don't start because of this issue. What I've seen, many quests are triggered by the first greeting, player choices and their subtopics. Any idea why? This bug or whatever is present everywhere; Capital Wasteland, Mojave Wasteland, DLC areas, mods (A World of Pain, standalone followers...).
Also, I had an issue with talking to Melody at The Fort where her dialogue doesn't have the "Goodbye." choice or any other way to terminate the dialogue, thus making the unmarked quest Saving (or Savaging) Sergeant Teddy impossible to complete.
