unfortunately, GnuPG 2.1.20 has a bug that can lead to keyring
corruptions when updating or deleting keys.
GnuPG supports two ways to store public keys. The classic one is the
'keyring' format. The new one is called a 'keybox'. Only the 'keyring'
format is affected. Long-term users will likely use the keyring format.
To find out whether you are using keyring or keybox, look into your
.gnupg directory. If a file named 'pubring.gpg' is present, you are
using the keyring format.
If you are using GnuPG 2.1.20 with the keyring format, a workaround is
to convert your keyring to a keybox. For this, follow: