Yes, now that you mention it, I believe I recall you set your campaign up this way, and me thinking that it may be a problem for you in the future.
I think it may relate to you having your campaign settings to DLGPartySwap to TRUE … BUT, I could be wrong and it be something completely different. (Also, it may be worth checking the NoCharacterChanging, as I have that as FALSE - I cannot recall what that did. )
Can you confirm if setting this to FALSE helps?
DID THIS HELP YOU BEFORE:
TRAVUS:
Set the NPC’s ‘Can Talk to Non-Player Owned Creatures’ property to TRUE.
OR
Use the SetCanTalkToNonPlayerOwnedCreatures(oObj, TRUE)
function for the NPC in a script.