Recently I have been setting up gnupg for a decently sized userbase. I notice
that the hack documented here https://www.sidorenko.io/blog/2014/11/04/yubikey-
slash-openpgp-smartcards-for-newbies/ (part relating to NOCARD event in scd-
event) is still required.
If there is an actual fix for this, I'd love to know. Otherwise, this seems
like a fairly common issue which should be better understood and fixed. Nearly
every guide I've seen about setting up gnupg has included something to this
effect. Mostly, people tell you to manually kill gpg-agent or related processes
when things don't appear to be working properly ... quite a sad state of
affairs.