A problem was reported where the option --rfc4880 does not seem to work after an update from Gpg4win 4.0.3 to 4.1.0
The user encrypted with option --rfc4880 and the recipient using the C# library bouncycastle tried to decrypt it.
When the file was encrypted with 4.0.3 the recipient could decrypt it. When it was encrypted with 4.1.0 the recipient could not decrypt it anymore. The recipient told that the problem was that "packet type 20" isn't part of the standard. The file was always encrypted using --rfc4880. The option --openpgp also didn't help.