[standalone@localhost:9990 /] /subsystem=ejb3:remove
{
    "outcome" => "success",
    "response-headers" => {
        "operation-requires-reload" => true,
        "process-state" => "reload-required"
    }
}
[standalone@localhost:9990 /] reload
[standalone@localhost:9990 /] /extension=org.jboss.as.ejb3:remove
{"outcome" => "success"}
[standalone@localhost:9990 /] /extension=org.jboss.as.ejb3:add   
{
    "outcome" => "failed",
    "failure-description" => "WFLYCTL0158: Operation handler failed: java.lang.IllegalArgumentException: WFLYCTL0218: A node is already registered at '/deployment=*/subdeployment=*/subsystem=ejb3'",
    "rolled-back" => true
}

13:46:48,278 ERROR [org.jboss.as.controller.management-operation] (management-handler-thread - 2) WFLYCTL0013: Operation ("add") failed - address: ([("extension" => "org.jboss.as.ejb3")]): java.lang.IllegalArgumentException: WFLYCTL0218: A node is already registered at '/deployment=*/subdeployment=*/subsystem=ejb3'
        at org.jboss.as.controller.registry.ConcreteResourceRegistration.registerSubModel(ConcreteResourceRegistration.java:222)
        at org.jboss.as.controller.extension.ExtensionRegistry$DeploymentManagementResourceRegistration.registerSubModel(ExtensionRegistry.java:922)
        at org.jboss.as.controller.extension.ExtensionRegistry$SubsystemRegistrationImpl.registerDeploymentModel(ExtensionRegistry.java:700)
        at org.jboss.as.ejb3.subsystem.EJB3Extension.initialize(EJB3Extension.java:91)
        at org.jboss.as.controller.extension.ExtensionAddHandler.initializeExtension(ExtensionAddHandler.java:131)
        at org.jboss.as.controller.extension.ExtensionAddHandler.execute(ExtensionAddHandler.java:83)
        at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:940)
        at org.jboss.as.controller.AbstractOperationContext.processStages(AbstractOperationContext.java:683)
        at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:382)
        at org.jboss.as.controller.OperationContextImpl.executeOperation(OperationContextImpl.java:1363)
        at org.jboss.as.controller.ModelControllerImpl.internalExecute(ModelControllerImpl.java:410)
        at org.jboss.as.controller.ModelControllerImpl.execute(ModelControllerImpl.java:232)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler.doExecute(ModelControllerClientOperationHandler.java:213)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler.access$300(ModelControllerClientOperationHandler.java:136)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1$1.run(ModelControllerClientOperationHandler.java:157)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1$1.run(ModelControllerClientOperationHandler.java:153)
        at java.security.AccessController.doPrivileged(Native Method)
        at javax.security.auth.Subject.doAs(Subject.java:422)
        at org.jboss.as.controller.AccessAuditContext.doAs(AccessAuditContext.java:149)
        at org.jboss.as.controller.remote.ModelControllerClientOperationHandler$ExecuteRequestHandler$1.execute(ModelControllerClientOperationHandler.java:153)
        at org.jboss.as.protocol.mgmt.ManagementRequestContextImpl$1.doExecute(ManagementRequestContextImpl.java:70)
        at org.jboss.as.protocol.mgmt.ManagementRequestContextImpl$AsyncTaskRunner.run(ManagementRequestContextImpl.java:160)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
        at java.lang.Thread.run(Thread.java:745)
        at org.jboss.threads.JBossThread.run(JBossThread.java:320)