In the first part of the quest, the following code is used to remove all items from the player and hide quest items:
PlayerRef.RemoveAllItems aaKOTNR14TempChest, 1SetShowQuestItems 1
At the end of the quest, the following code is used to replace them:
aaKOTNR14TempChest.RemoveAllItems PlayerRef, 1SetShowQuestItems 0
Weapons that have been reported to be duplicated include Umbra, Rockshatter and the Akavari Blade from an Enhanced Economy quest.
I was unable to replicate the problem using Rockshatter. Checking the contents of aaKOTNR14TempChest and SetShowQuestItems 0 verifies that Rockshatter was still in my inventory and didn't get duplicated. Nor did I get an extra copy of the weapon when the quest finished.
Is anyone aware of any glitches that may explain this bug?