admin で Claim しようとするとエラーになる。Organizational entity already exists

admin で Claim しようとするとエラーになる。

2017-02-23 15:15:19,268 ERROR [org.kie.server.remote.rest.jbpm.UserTaskResource] (default task-63) Unexpected error during processing Organizational entity already exists with [UserImpl:'admin'] id, please check that there is no group and user with same id: java.lang.RuntimeException: Organizational entity already exists with [UserImpl:'admin'] id, please check that there is no group and user with same id
 at org.jbpm.services.task.persistence.JPATaskPersistenceContext.persistOrgEntity(JPATaskPersistenceContext.java:240)
 at org.jbpm.services.task.commands.UserGroupCallbackTaskCommand.persistIfNotExists(UserGroupCallbackTaskCommand.java:143)

admin 以外のユーザーで Claim しましょう。