Are you looting more than one backpack of non-stackables per refill? I guess I that could happen if you did and there weren't any sellable loot in the currently opened one. I should add a backpack reset before checking the npcs. If it isn't that, then maybe there's a chance that the npc was out of range. That guy has a huge counter so I guess it could be possible. If that's the issue dealing with it will require some specialized lua.