This is a long standing bug (only occurs in the transition of changing by "forcesig", though).
To reproduce (assumption is it's "force" state for signing authentication):
$ gpg --clearsign -v some.txt && rm -f some.txt.asc # Success here, card implementation resets its authentication state after signing, # But GnuPG considers wrongly card auth state is still "authenticated" $ gpg --card-edit gpg/card> admin gpg/card> forcesig # this makes card "not forced" gpg/card> quit $ gpg --clearsign some.txt # Here, the card actually require authentication, but GnuPG wrongly considers it's not needed, so... signing failed: Bad PIN # The card behavior is correct rejecting signing