create new folder under stress gives error

While testing the test server with two browsers simultaneously CMS give after a while the following error when creating a new folder:

javax.jcr.RepositoryException: Unable to update item: node /: 7b90f7d5-5a60-4c85-8d43-0f098733da1e: 7b90f7d5-5a60-4c85-8d43-0f098733da1e

javax.jcr.RepositoryException: Unable to update item: node /: 7b90f7d5-5a60-4c85-8d43-0f098733da1e: 7b90f7d5-5a60-4c85-8d43-0f098733da1e
at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1111)
at org.apache.jackrabbit.core.SessionImpl.save(SessionImpl.java:846)
at org.hippoecm.repository.decorating.SessionDecorator.save(SessionDecorator.java:202)
at org.hippoecm.repository.impl.SessionDecorator.save(SessionDecorator.java:153)
at org.hippoecm.repository.standardworkflow.FolderWorkflowImpl.add(FolderWorkflowImpl.java:243)
at org.hippoecm.repository.standardworkflow.FolderWorkflowImpl.add(FolderWorkflowImpl.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hippoecm.repository.impl.WorkflowManagerImpl$WorkflowInvocationHandler.invoke(WorkflowManagerImpl.java:508)
at $Proxy4.add(Unknown Source)
at org.hippoecm.frontend.plugins.standardworkflow.FolderWorkflowPlugin$4.execute(FolderWorkflowPlugin.java:230)
at org.hippoecm.frontend.plugins.standardworkflow.FolderWorkflowPlugin$4.execute(FolderWorkflowPlugin.java:206)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction.execute(CompatibilityWorkflowPlugin.java:142)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction$WorkflowDialog.execute(CompatibilityWorkflowPlugin.java:216)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction$WorkflowDialog.onOk(CompatibilityWorkflowPlugin.java:201)
at org.hippoecm.frontend.dialog.AbstractDialog.handleSubmit(AbstractDialog.java:500)
at org.hippoecm.frontend.dialog.AbstractDialog$2.onSubmit(AbstractDialog.java:377)
at org.hippoecm.frontend.dialog.AbstractDialog$ButtonWrapper$1.onSubmit(AbstractDialog.java:251)
at org.apache.wicket.ajax.markup.html.form.AjaxButton$1.onSubmit(AjaxButton.java:86)
at org.apache.wicket.ajax.form.AjaxFormSubmitBehavior.onEvent(AjaxFormSubmitBehavior.java:128)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:163)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:297)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(BehaviorRequestTarget.java:100)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:91)
at org.hippoecm.frontend.Main$6.processEvents(Main.java:287)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1175)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1252)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1353)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:493)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:355)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:200)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)
Caused by: org.apache.jackrabbit.core.state.NoSuchItemStateException: 7b90f7d5-5a60-4c85-8d43-0f098733da1e
at org.apache.jackrabbit.core.state.SharedItemStateManager.getItemState(SharedItemStateManager.java:269)
at org.apache.jackrabbit.core.state.SharedItemStateManager$Update.begin(SharedItemStateManager.java:587)
at org.apache.jackrabbit.core.state.SharedItemStateManager.beginUpdate(SharedItemStateManager.java:1054)
at org.apache.jackrabbit.core.state.SharedItemStateManager.update(SharedItemStateManager.java:1084)
at org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:337)
at org.apache.jackrabbit.core.state.XAItemStateManager.update(XAItemStateManager.java:340)
at org.hippoecm.repository.jackrabbit.HippoLocalItemStateManager.update(HippoLocalItemStateManager.java:219)
at org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:312)
at org.hippoecm.repository.jackrabbit.HippoLocalItemStateManager.update(HippoLocalItemStateManager.java:226)
at org.apache.jackrabbit.core.state.SessionItemStateManager.update(SessionItemStateManager.java:313)
at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1105)
... 47 more
org.apache.jackrabbit.core.state.NoSuchItemStateException: 7b90f7d5-5a60-4c85-8d43-0f098733da1e
at org.apache.jackrabbit.core.state.SharedItemStateManager.getItemState(SharedItemStateManager.java:269)
at org.apache.jackrabbit.core.state.SharedItemStateManager$Update.begin(SharedItemStateManager.java:587)
at org.apache.jackrabbit.core.state.SharedItemStateManager.beginUpdate(SharedItemStateManager.java:1054)
at org.apache.jackrabbit.core.state.SharedItemStateManager.update(SharedItemStateManager.java:1084)
at org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:337)
at org.apache.jackrabbit.core.state.XAItemStateManager.update(XAItemStateManager.java:340)
at org.hippoecm.repository.jackrabbit.HippoLocalItemStateManager.update(HippoLocalItemStateManager.java:219)
at org.apache.jackrabbit.core.state.LocalItemStateManager.update(LocalItemStateManager.java:312)
at org.hippoecm.repository.jackrabbit.HippoLocalItemStateManager.update(HippoLocalItemStateManager.java:226)
at org.apache.jackrabbit.core.state.SessionItemStateManager.update(SessionItemStateManager.java:313)
at org.apache.jackrabbit.core.ItemImpl.save(ItemImpl.java:1105)
at org.apache.jackrabbit.core.SessionImpl.save(SessionImpl.java:846)
at org.hippoecm.repository.decorating.SessionDecorator.save(SessionDecorator.java:202)
at org.hippoecm.repository.impl.SessionDecorator.save(SessionDecorator.java:153)
at org.hippoecm.repository.standardworkflow.FolderWorkflowImpl.add(FolderWorkflowImpl.java:243)
at org.hippoecm.repository.standardworkflow.FolderWorkflowImpl.add(FolderWorkflowImpl.java:179)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.hippoecm.repository.impl.WorkflowManagerImpl$WorkflowInvocationHandler.invoke(WorkflowManagerImpl.java:508)
at $Proxy4.add(Unknown Source)
at org.hippoecm.frontend.plugins.standardworkflow.FolderWorkflowPlugin$4.execute(FolderWorkflowPlugin.java:230)
at org.hippoecm.frontend.plugins.standardworkflow.FolderWorkflowPlugin$4.execute(FolderWorkflowPlugin.java:206)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction.execute(CompatibilityWorkflowPlugin.java:142)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction$WorkflowDialog.execute(CompatibilityWorkflowPlugin.java:216)
at org.hippoecm.addon.workflow.CompatibilityWorkflowPlugin$WorkflowAction$WorkflowDialog.onOk(CompatibilityWorkflowPlugin.java:201)
at org.hippoecm.frontend.dialog.AbstractDialog.handleSubmit(AbstractDialog.java:500)
at org.hippoecm.frontend.dialog.AbstractDialog$2.onSubmit(AbstractDialog.java:377)
at org.hippoecm.frontend.dialog.AbstractDialog$ButtonWrapper$1.onSubmit(AbstractDialog.java:251)
at org.apache.wicket.ajax.markup.html.form.AjaxButton$1.onSubmit(AjaxButton.java:86)
at org.apache.wicket.ajax.form.AjaxFormSubmitBehavior.onEvent(AjaxFormSubmitBehavior.java:128)
at org.apache.wicket.ajax.AjaxEventBehavior.respond(AjaxEventBehavior.java:163)
at org.apache.wicket.ajax.AbstractDefaultAjaxBehavior.onRequest(AbstractDefaultAjaxBehavior.java:297)
at org.apache.wicket.request.target.component.listener.BehaviorRequestTarget.processEvents(BehaviorRequestTarget.java:100)
at org.apache.wicket.request.AbstractRequestCycleProcessor.processEvents(AbstractRequestCycleProcessor.java:91)
at org.hippoecm.frontend.Main$6.processEvents(Main.java:287)
at org.apache.wicket.RequestCycle.processEventsAndRespond(RequestCycle.java:1175)
at org.apache.wicket.RequestCycle.step(RequestCycle.java:1252)
at org.apache.wicket.RequestCycle.steps(RequestCycle.java:1353)
at org.apache.wicket.RequestCycle.request(RequestCycle.java:493)
at org.apache.wicket.protocol.http.WicketFilter.doGet(WicketFilter.java:355)
at org.apache.wicket.protocol.http.WicketFilter.doFilter(WicketFilter.java:200)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.hippoecm.frontend.plugins.login.ConcurrentLoginFilter.doFilter(ConcurrentLoginFilter.java:54)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:286)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:845)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:447)
at java.lang.Thread.run(Unknown Source)