After configuring sellitem-jsf with the correct set of .jars (including backport-concurrent, fileupload, el-api) fixing unclosed img tags in the source, and mapping all .jsp to PersistentFacesServlet, the following exception is thrown (although the application seems functional):

java.lang.IllegalMonitorStateException
        at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:125)
        at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1102)
        at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:431)
        at org.springframework.webflow.conversation.impl.JdkConcurrentConversationLock.unlock(JdkConcurrentConversationLock.java:40)
        at org.springframework.webflow.conversation.impl.ContainedConversation.unlock(ContainedConversation.java:104)
        at org.springframework.webflow.execution.repository.support.ConversationBackedFlowExecutionLock.unlock(ConversationBackedFlowExecutionLock.java:58)
        at org.springframework.webflow.executor.jsf.FlowPhaseListener.afterPhase(FlowPhaseListener.java:249)
        at org.apache.myfaces.lifecycle.PhaseListenerManager.informPhaseListenersAfter(PhaseListenerManager.java:89)
        at org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:391)
        at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.renderCycle(ReceiveSendUpdates.java:58)
        at com.icesoft.faces.webapp.http.core.ReceiveSendUpdates.service(ReceiveSendUpdates.java:45)
        at com.icesoft.faces.webapp.http.core.IDVerifier.service(IDVerifier.java:19)
        at com.icesoft.faces.webapp.http.servlet.BasicAdaptingServlet.service(BasicAdaptingServlet.java:16)
        at com.icesoft.faces.webapp.http.servlet.ViewBoundAdaptingServlet.service(ViewBoundAdaptingServlet.java:30)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher$Matcher.serviceOnMatch(PathDispatcher.java:53)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:29)
        at com.icesoft.faces.webapp.http.servlet.MainSessionBoundServlet.service(MainSessionBoundServlet.java:89)
        at com.icesoft.faces.webapp.http.servlet.SessionDispatcher.service(SessionDispatcher.java:35)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher$Matcher.serviceOnMatch(PathDispatcher.java:53)
        at com.icesoft.faces.webapp.http.servlet.PathDispatcher.service(PathDispatcher.java:29)
        at com.icesoft.faces.webapp.http.servlet.MainServlet.service(MainServlet.java:60)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
        at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:704)
        at org.apache.catalina.core.ApplicationDispatcher.processRequest(ApplicationDispatcher.java:474)
        at org.apache.catalina.core.ApplicationDispatcher.doForward(ApplicationDispatcher.java:370)
        at org.apache.catalina.core.ApplicationDispatcher.forward(ApplicationDispatcher.java:312)
        at com.icesoft.faces.webapp.xmlhttp.BlockingServlet.service(BlockingServlet.java:54)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:237)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:157)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:214)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardContextValve.invokeInternal(StandardContextValve.java:198)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:152)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:137)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:118)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:102)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
        at org.apache.catalina.core.StandardValveContext.invokeNext(StandardValveContext.java:104)
        at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:520)
        at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:929)
        at org.apache.coyote.tomcat5.CoyoteAdapter.service(CoyoteAdapter.java:160)
        at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:799)
        at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:705)
        at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:577)
        at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:683)
        at java.lang.Thread.run(Thread.java:613)