[keycloak-user] server hang on adding admin user

I'm get a strange and infrequent problem when I add the admin user to keycloak. I'm running keycloak inside a docker container (the jboss/keycloak-postgres:1.9.1.Final image), and I add the admin user using the KEYCLOAK_USER and KEYCLOAK_PASSWORD environment variables set the first time the container is started. Occasionally the server seems to hang and the docker container can't bet stopped or even killed. The logs show this: keycloak_1 | 10:56:19,876 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0060: Http management interface listening on http://127.0.0.1:9990/management keycloak_1 | 10:56:19,876 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0051: Admin console listening on http://127.0.0.1:9990 keycloak_1 | 10:56:19,877 INFO [org.jboss.as] (Controller Boot Thread) WFLYSRV0025: Keycloak 1.9.1.Final (WildFly Core 2.0.10.Final) started in 12810ms - Started 422 of 789 services (529 services are lazy, passive or on-demand) keycloak_1 | keycloak_1 | Added 'admin' to '/opt/jboss/keycloak/standalone/configuration/keycloak-add-user.json', restart server to load user Seem like keycloak adds the admin user then gives up on life completely and can't be stopped. This only happens occasionally, but frequently enough to be a problem. Any ideas what's happening here? Tim