I can log in as demo user Mike and create two orders and add an item to each order. Then, I can log in as Brenda, add new items to each order and checkout.
However, if I log in as Brenda, create new orders, add items to each cart and then log in as Mike I am unable to do the same thing. As Mike I can see the two orders that Brenda created but Mike can't add any items to those carts.
Mike should be able to add to the order because he’s a Buyer on the Account.