XComGameState_HeadQuartersXCom::AddSeenCharacterTemplate and HasSeenCharacterTemplate functions add the character group to the array of seen template names, not the individual templates.

This means that for various advent units (trooperm2/m3, lancerm2/m3 and various others), where a specific narrative moment is described but the character group has already been seen, the narrative moment which is supposed to play when these units are first sighted, doesn't.

This can be confirmed by testing in TQL/Skirmish+ and dropping one of the affected units into play. Using SetFirstSeenVODisabled false may help if using any other mods which disables narrative stuff.

function AddSeenCharacterTemplate(X2CharacterTemplate CharacterTemplate)
{
	SeenCharacterTemplates.AddItem(CharacterTemplate.CharacterGroupName);
}

function bool HasSeenCharacterTemplate(X2CharacterTemplate CharacterTemplate)
{
	return (SeenCharacterTemplates.Find(CharacterTemplate.CharacterGroupName) != INDEX_NONE);
}

Suggested fix would be to somehow gather an array of 'played narrative moments', switch these functions over to using the character templates directly and simply exclude narrative moments that have already been played.