My son (6 yrs old) and I finished Encore earlier today. For some reason, I received the Exotic weapon CHOIR OF ONE and he did not. We're not sure if this was because his Post Office was almost full or because he wasn't as far in the Seasonal campaign missions, but this is the first time we ever completed an Exotic mission together and he did not receive the intended Weapon reward. He is beyond frustrated, at this point. He received ALL of the other rewards for the mission, including 3 or 4 red border season legendaries. But somehow not the Exotic.