ERROR occured when I call APIM Rest API. (in multiple user) - wso2

Question

I use WSO2 API-Manager 2.1.0 with MaribDB.
Recently I've done some test with APIM Rest APIs such as create api, change life-cycle, and create application.
The point of my test was to check how to APIM work when receive multiple requests.
so I made a situation that 10 users call same RestAPI at the same time.
During the test, I faced to unexpected ERROR. However I coundn't found out what cause that kind of ERROR.
so I changed some code(am#api#publisher) to make them work synchronized.
I got the result with less ERROR but them still occrued.
Can somebody give me some advise? ( Please check the ERROR Log)
TID: [-1234] [] [2018-07-03 13:41:49,736] ERROR {org.wso2.carbon.apimgt.impl.executors.APIExecutor} - Failed to get the generic artifact while executing APIExecutor. {org.wso2.carbon.apimgt.impl.executors.APIExecutor}
org.wso2.carbon.governance.api.exception.GovernanceException: Invalid check list item.
at org.wso2.carbon.governance.api.common.dataobjects.GovernanceArtifactImpl.isLCItemChecked(GovernanceArtifactImpl.java:897)
at org.wso2.carbon.apimgt.impl.executors.APIExecutor.execute(APIExecutor.java:170)
at org.wso2.carbon.governance.registry.extensions.aspects.DefaultLifeCycle.runCustomExecutorsCode(DefaultLifeCycle.java:712)
at org.wso2.carbon.governance.registry.extensions.aspects.DefaultLifeCycle.invoke(DefaultLifeCycle.java:450)
at org.wso2.carbon.governance.registry.eventing.handlers.GovernanceEventingHandler.invokeAspect(GovernanceEventingHandler.java:338)
at org.wso2.carbon.registry.core.jdbc.handlers.HandlerManager.invokeAspect(HandlerManager.java:2792)
at org.wso2.carbon.registry.core.jdbc.handlers.HandlerLifecycleManager.invokeAspect(HandlerLifecycleManager.java:518)
at org.wso2.carbon.registry.core.jdbc.EmbeddedRegistry.invokeAspect(EmbeddedRegistry.java:2591)
at org.wso2.carbon.registry.core.caching.CacheBackedRegistry.invokeAspect(CacheBackedRegistry.java:510)
at org.wso2.carbon.registry.core.session.UserRegistry.invokeAspect(UserRegistry.java:1952)
at org.wso2.carbon.governance.api.common.dataobjects.GovernanceArtifactImpl.invokeAction(GovernanceArtifactImpl.java:829)
at org.wso2.carbon.governance.api.common.dataobjects.GovernanceArtifactImpl.invokeAction(GovernanceArtifactImpl.java:808)
at org.wso2.carbon.apimgt.impl.APIProviderImpl.changeLifeCycleStatus(APIProviderImpl.java:3755)
at org.wso2.carbon.apimgt.impl.UserAwareAPIProvider.changeLifeCycleStatus(UserAwareAPIProvider.java:148)
at org.wso2.carbon.apimgt.rest.api.publisher.impl.ApisApiServiceImpl.apisChangeLifecyclePost(ApisApiServiceImpl.java:303)
at org.wso2.carbon.apimgt.rest.api.publisher.ApisApi.apisChangeLifecyclePost(ApisApi.java:520)
at sun.reflect.GeneratedMethodAccessor241.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.cxf.service.invoker.AbstractInvoker.performInvocation(AbstractInvoker.java:180)
at org.apache.cxf.service.invoker.AbstractInvoker.invoke(AbstractInvoker.java:96)
at org.apache.cxf.jaxrs.JAXRSInvoker.invoke(JAXRSInvoker.java:189)
at org.apache.cxf.jaxrs.JAXRSInvoker.invoke(JAXRSInvoker.java:99)
at org.apache.cxf.interceptor.ServiceInvokerInterceptor$1.run(ServiceInvokerInterceptor.java:59)
at org.apache.cxf.interceptor.ServiceInvokerInterceptor.handleMessage(ServiceInvokerInterceptor.java:96)
at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:308)
at org.apache.cxf.transport.ChainInitiationObserver.onMessage(ChainInitiationObserver.java:121)
at org.apache.cxf.transport.http.AbstractHTTPDestination.invoke(AbstractHTTPDestination.java:254)
at org.apache.cxf.transport.servlet.ServletController.invokeDestination(ServletController.java:234)
at org.apache.cxf.transport.servlet.ServletController.invoke(ServletController.java:208)
at org.apache.cxf.transport.servlet.ServletController.invoke(ServletController.java:160)
at org.apache.cxf.transport.servlet.CXFNonSpringServlet.invoke(CXFNonSpringServlet.java:180)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.handleRequest(AbstractHTTPServlet.java:299)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.doPost(AbstractHTTPServlet.java:218)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
at org.apache.cxf.transport.servlet.AbstractHTTPServlet.service(AbstractHTTPServlet.java:274)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.continueInvocation(CompositeValve.java:99)
at org.wso2.carbon.tomcat.ext.valves.CarbonTomcatValve$1.invoke(CarbonTomcatValve.java:47)
at org.wso2.carbon.webapp.mgt.TenantLazyLoaderValve.invoke(TenantLazyLoaderValve.java:57)
at org.wso2.carbon.event.receiver.core.internal.tenantmgt.TenantLazyLoaderValve.invoke(TenantLazyLoaderValve.java:48)
at org.wso2.carbon.tomcat.ext.valves.TomcatValveContainer.invokeValves(TomcatValveContainer.java:47)
at org.wso2.carbon.tomcat.ext.valves.CompositeValve.invoke(CompositeValve.java:62)
at org.wso2.carbon.tomcat.ext.valves.CarbonStuckThreadDetectionValve.invoke(CarbonStuckThreadDetectionValve.java:159)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:958)
at org.wso2.carbon.tomcat.ext.valves.CarbonContextCreatorValve.invoke(CarbonContextCreatorValve.java:57)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1756)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1715)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)