This has been happening on one of my private git repos since around the beginning of this week (only on macOS 10.13.3):

$ git pull
Initializing Keybase... done.
Syncing with Keybase... done.
git-remote-keybase error: (1) packfile not found

The first time this happened, I upgraded Keybase to Version 1.0.47-20180410052738+f705a9510f. However, I'm continuing to see this happen. I saw #11358 and tried to run keybase git delete $REPO, since I have the repo cloned locally, but that command hangs.