So I'm working on expanding my mod, Serana Dialogue Expansion, and decided to add a quick scene between Serana and Alva in Morthal. Well, the scene starts, all well and good, but at the start of the scene, only Serana speaks. Alva's dialogues are just skipped. I triple-checked the references, the dialogues and everything, and all seems well. Other NPCs have the same boxes checked and it works with them perfectly, but Alva is, for some reason, the rare exception and won't even be acknowledged in the conversation.
Has this ever happened to you? Do you know what might be causing this, and if other NPCs are affected?