Missing audio from various NPC in the game. Idle dialogue or missions pickup/completion is not playing. This issues seem to have started sometime during season 3, season 4 or season 5.
The following audio issues are instances I have encountered myself, there may be more throughout the game.
# MLK Community Library - The person giving the quest has his dialogue missing when picking this quest up.
# Missing Curators - The two people giving this quest have their dialogue missing when picking this quest up.
# Missing Wire Scavengers - The person giving this quest has her dialogue missing when picking this quest up.
# Return to Haven - Agent Kelso has her dialogue missing when the mission is turned in.
# The NPC that lets you into the Air and Space museum, at the start of the mission, has her dialogue missing.
# Upgrading theater settlement to tier 3 adds two NPC talking about the blimp, this dialogue does not play.
# The Sister in The Ark quarantine zone walks around, instead of sitting by the injured person, this causes dialogue issues.
# The NPC you have to rescue during the Roosevelt Stronghold mission should talk to a guy behind a gate. This not happen.
# The True Sons random encounter, where a the soldier does push ups and an other says their grandma can do better has no dialogue.
# Outcast random encounter with an outcast shouting through a megaphone to other outcast has no dialogue.
# Sometimes when encountering the Hunter Stalkers in the world the distortion sound effect goes missing.