I think there is a problem with the secret key import/export on windows machines. I
wanted to transfer a secret key from one windows machine to another. I used the following
commands:

On my origin computer:
Attempt 1: Using GPA: Keys->Backup...
Attempt 2: Commandline: gpg --export-secret-key -a > secret.key

On the receiving computer:
Attempt 1: Using GPA: Keys->Import Keys...
Attempt 2: Commandline: gpg --allow-secret-key-import --import secret.key

Every time, the secret key import failed. GPA and commandline said that no secret keys
could be imported. I verified this using the "gpg -K" command.

When dropping the "-a" flag from the export command, everything worked. This leads me to
suspect some error related to the output format...

My system specs:

• Windows 7 (both computers)
• Origin computer: GnuPG modern: gnupg-w32-2.1.1_20141216.exe
• Receiving computer: Tried both with GnuPG modern 2.1.1 and GnuPG: Gpg4win stable 2.2.3