This issue was caused by the removal of --graph in https://docs.docker.com/engine/release-notes/23.0/#2300. Unfortunately it does not appear that the existing use of the deprecated option resulted in any warnings, thus this was not noticed.
More information at https://docs.docker.com/engine/deprecated/#-g-and---graph-flags-on-dockerd.
Obviously, this only resulted in an outage because maintenance was performed directly on the production instance. The inability to deploy changes properly is a result of https://github.com/radian-software/riju/issues/168 and will be resolved by migrating to Kubernetes as outlined in that issue.
A fix has been retroactively pushed into version control at https://github.com/radian-software/riju/commit/23fc1617f4e8a3f5969c5aa0853e65b36a2e358d.