Once you've killed Gathbin's guys in tavern and you return to Caed Nua, Marshal Forwyn waits in the main hall to inform you about Gathbin's preparations.

 

However, a couple of days later, a second Marshal Forwyn spawned outside of the tower, together with the scripted crowd that you can pay off earlier in the quest.

 

I've beat Gathbin's army, and the Marshal in the main hall is gone, but the one outside with the crowd remains, and while he has the same dialogue options as the other one, none of them do anything.

I've also just ran into this, although I'm not sure I've ever seen this crowd outside of my keep.  Just returned to my stronghold to fight off some bandits, and noticed them there after the fight (no idea if they were there before as I initiated the manual resolution as soon as I entered town).

 

I've attached a picture!

fun fact: you don't lose any reputation if you kill the extra ones 

Hey guys!

 

Welcome and thanks for joining us! This is a known issue and it has been fixed and will be in the next 3.02 patch!

 

Thanks a bunch!