The copr build service is using gnupg2 to extend the validity of the signing keys using
sequence. The exported key contains only the new signature. This is likely ok for email usage, but it is problematic for RPM usage as we still want to keep trusting the signatures made before the validity extension without the need to re-sign everything.
It might be that copr is doing something wrong and there is other/better/preferred way to extend key validity using gpg tools so any help/pointer welcomed.