Open Order allocation issue

We're running into issues when trying to process delivery requests for Open Orders. We will have exactly enough stock of a product in the system that is on a delivery request for an Open Order, the stock will ONLY be allocated to that Open Order, but when we try to create a delivery for that Open Order/delivery request the system will give us an error message saying "The quantity to be delivered is in shortage and negative stock is prohibited, or shortage quantities are not deliverable." Even though the stock is allocated to that specific order, we have to deallocate the stock to make it "available" to then be able to create a delivery for that same order...  

Why would X3 say we have negative stock or no stock available for an order when we have the exact amount and it's even allocated to that specific order?