What I dont understand is that if someone posts a request for items and you try to send one and get the error then the item is not sent and remains in your inventory. However if you send a collection item to an ally then your count for that item increases by 1 and theirs too unless the error is generated in which case your count increases and they dont receive the post. Maybe if a solution to this cannot be found and it is a Facebook issue then you could make it like a requested item i.e. if the error is generated then neither of you receive the item, and the collection item remains so at least you can try again to send it.