There’s defintiely several instances where I can think of where dialogue is being cut due to the way checkpoints are reached with a group of people, such as the dialogue between the thrall at the bottom of the elevator in The Sentinel mission. I’ve only ever heard it from “…that’s fine third time’s the charm” which is sorta random without the first part of the conversation.
I would recommend people read up on the dialogue and point out where certain dialogue cues are failing so they can get put on a todo list for the far far future, even if its a low priority thing, we can at least make the devs aware of them 
(I would also be keen if people could identify which characters are needed to trigger character specific lines so I can add this to my dialogue page)