^C agents process running under zookeeper when under load causes exception

Exception in thread "Shutdown thread" java.lang.IllegalStateException: Already have a lock in place: '/org.apache.manifoldcf.locks-_Cache_JOB_1386770226340/read
-0000000317'; can't also write lock '/org.apache.manifoldcf.servicelock-AGENT_org.apache.manifoldcf.crawler.system.CrawlerAgent'
        at org.apache.manifoldcf.core.lockmanager.ZooKeeperConnection.obtainWriteLockNoWait(ZooKeeperConnection.java:265)
        at org.apache.manifoldcf.core.lockmanager.ZooKeeperLockManager.enterServiceRegistryWriteLock(ZooKeeperLockManager.java:551)
        at org.apache.manifoldcf.core.lockmanager.ZooKeeperLockManager.endServiceActivity(ZooKeeperLockManager.java:473)
        at org.apache.manifoldcf.agents.system.AgentsDaemon.stopAgents(AgentsDaemon.java:169)
        at org.apache.manifoldcf.agents.system.AgentsDaemon$AgentsShutdownHook.doCleanup(AgentsDaemon.java:385)
        at org.apache.manifoldcf.core.system.ManifoldCF.cleanUpEnvironment(ManifoldCF.java:1306)
        at org.apache.manifoldcf.core.system.ManifoldCF$ShutdownThread.run(ManifoldCF.java:1460)