If a message has multiple PGPPublicKeyEncryptedData (meaning, multiple recipients), PGPDataFormat fails to decrypt the message (unless our key is the first PGPPublicKeyEncryptedData element).
Said differently, if a message is encrypted for recipient A and B (and the encrypted parts are in that order) and we are recipient B, the message fails to decrypt.
This definitely affected version 2.11.1. Looking at the latest version of the same files, this is most likely still an issue. The fix in the patch that will be supplied is currently being used in our application, but unfortunately I do not have a test case available.
I will create a pull-request on Github shortly.