Not sure why, but it seems that sometimes the judgehosts get interrupted before they've had time to install everything, which leaves them in a corrupted state. Fixing this may require changing the judge Docker image to not die when the judging daemon dies.
Easiest fix: change --entrypoint in docker run to install the stuff first; but make sure this doesn't cause problems if it has to restart, maybe a self-destructing script.
Not sure why, but it seems that sometimes the judgehosts get interrupted before they've had time to install everything, which leaves them in a corrupted state. Fixing this may require changing the judge Docker image to not die when the judging daemon dies.