This is a long post, but due to the severity of the situation, it warrants a full and thorough explanation. tl;dr : Paypal has a mission critical bug with their Adaptive Payments API that has been live for at least 9 days, and did not even know. Today we received an email from a customer that was concerned his order wasn't showing up under his account, yet it was visible on his Paypal account. After digging into our implementation of Paypal's Adaptive Payments API, we didn't find anything wron...