When a message has been encrypted to multiple recipients (-r user1 -r user2 ...)
decryption tries to use the available secret keys in arbitrary order.
Apparently there is no clean of specifying which secret key should be used,
especially if only the passphrase of a single key is currently known.
see also
http://stackoverflow.com/questions/19562185/gpg-decrypt-with-multiple-recipients
Is there any good reason why one cannot specify the key for decoding with -u or -r?
You have the problem only if hidden recipients are used. With 2.1 you
may use this option:
--try-secret-key name
For hidden recipients GPG needs to know the keys to use for trial
decryption. The key set with --default-key is always tried first,
but this is often not sufficient. This option allows to set more
keys to be used for trial decryption. Although any valid user-id
specifica- tion may be used for name it makes sense to use at
least the long keyid to avoid ambiguities. Note that gpg-agent
might pop up a pinentry for a lot keys to do the trial decryption.
If you want to stop all further trial decryption you may use
close-window button instead of the cancel button.This won't be backported to 2.0.
The reporter wasn't to specify the secret key to use. Werner indicated that
--try-secret-key does what the reporter wants in 2.1, but that this won't be
backported to 2.0. As such, I'm marking this issue as resolved.