Comment 11 for bug 1777710

So yeah, my suggestion to reimport public key was right. It is an odd corner case. I think it has to do with something how the upstream choose to reorganize public & secret keyrings; such that the split of which bits need to be where is now different, and the export of old is either incomplete for what the new one wants or the new one does import all the right things during migration.

I think it is prudent to refresh / have an up to date public key, wherever private keys are. I've seen this trip up a few people, but it is a bit of a self-service that one must do when migrating to 2.1 unfortunately.

It could be "fixed" by automatic refreshing of public keys.... but we are not going to do that.