Problem initializing plan model for snapshot: NullPointer

Hi,
I'm getting the following error when trying to take a plan snapshot when using the Web UI.
I'm using RTC 3.0 and I've created a customized process. I have already reviewed all workflow but couldn't find anything wrong, the states, actions and groups seems correct. I don't get any error to create work items and change the states also no errors to view the plan in any kind of view (taskboard, Ranked List, Work Breakdown). The error only occur when clicking on snapshot tab.

Problem in initializing plan model for snapshot: java.lang.NullPointerException
java.lang.NullPointerException
com.ibm.team.apt.internal.service.rest.serialize.StateTransitionSerializable.getItemId(StateTransitionSerializable.java:44)
com.ibm.team.apt.internal.service.rest.serialize.AbstractWebUISerializable.hashCode(AbstractWebUISerializable.java:22)
java.util.HashMap.getEntry(HashMap.java:510)
java.util.HashMap.containsKey(HashMap.java:433)
com.ibm.team.apt.internal.service.rest.serialize.WebUISerializer.getReference(WebUISerializer.java:697)
com.ibm.team.apt.internal.service.rest.serialize.WebUISerializer.stateTransition(WebUISerializer.java:663)
com.ibm.team.apt.internal.service.rest.PlanRestService.postGetStateTransition(PlanRestService.java:1669)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
java.lang.reflect.Method.invoke(Method.java:611)
org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.invoke(ExportProxyServiceRecord.java:370)
org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord.access$0(ExportProxyServiceRecord.java:356)
org.eclipse.soda.sat.core.internal.record.ExportProxyServiceRecord$ExportedServiceInvocationHandler.invoke(ExportProxyServiceRecord.java:56)
$Proxy447.postGetStateTransition(Unknown Source)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
java.lang.reflect.Method.invoke(Method.java:611)
com.ibm.team.repository.servlet.AbstractTeamServerServlet.doModelledRestService(AbstractTeamServerServlet.java:501)
com.ibm.team.repository.servlet.AbstractTeamServerServlet.handleRequest2(AbstractTeamServerServlet.java:1832)
com.ibm.team.repository.servlet.AbstractTeamServerServlet.handleRequest(AbstractTeamServerServlet.java:1688)
com.ibm.team.repository.servlet.AbstractTeamServerServlet.service(AbstractTeamServerServlet.java:1598)
javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
org.eclipse.equinox.http.registry.internal.ServletManager$ServletWrapper.service(ServletManager.java:180)
org.eclipse.equinox.http.servlet.internal.ServletRegistration.handleRequest(ServletRegistration.java:90)
org.eclipse.equinox.http.servlet.internal.ProxyServlet.processAlias(ProxyServlet.java:111)
org.eclipse.equinox.http.servlet.internal.ProxyServlet.service(ProxyServlet.java:75)
javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
org.eclipse.equinox.servletbridge.BridgeServlet.service(BridgeServlet.java:120)
com.ibm.team.repository.server.servletbridge.JazzServlet.service(JazzServlet.java:62)
javax.servlet.http.HttpServlet.service(HttpServlet.java:831)
com.ibm.ws.webcontainer.servlet.ServletWrapper.service(ServletWrapper.java:1657)
com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:939)
com.ibm.ws.webcontainer.servlet.ServletWrapper.handleRequest(ServletWrapper.java:502)
com.ibm.ws.webcontainer.servlet.ServletWrapperImpl.handleRequest(ServletWrapperImpl.java:179)
com.ibm.ws.webcontainer.servlet.CacheServletWrapper.handleRequest(CacheServletWrapper.java:91)
com.ibm.ws.webcontainer.WebContainer.handleRequest(WebContainer.java:864)
com.ibm.ws.webcontainer.WSWebContainer.handleRequest(WSWebContainer.java:1583)
com.ibm.ws.webcontainer.channel.WCChannelLink.ready(WCChannelLink.java:186)
com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleDiscrimination(HttpInboundLink.java:445)
com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.handleNewRequest(HttpInboundLink.java:504)
com.ibm.ws.http.channel.inbound.impl.HttpInboundLink.processRequest(HttpInboundLink.java:301)
com.ibm.ws.http.channel.inbound.impl.HttpICLReadCallback.complete(HttpICLReadCallback.java:83)
com.ibm.ws.ssl.channel.impl.SSLReadServiceContext$SSLReadCompletedCallback.complete(SSLReadServiceContext.java:1784)
com.ibm.ws.tcp.channel.impl.AioReadCompletionListener.futureCompleted(AioReadCompletionListener.java:165)
com.ibm.io.async.AbstractAsyncFuture.invokeCallback(AbstractAsyncFuture.java:217)
com.ibm.io.async.AsyncChannelFuture.fireCompletionActions(AsyncChannelFuture.java:161)
com.ibm.io.async.AsyncFuture.completed(AsyncFuture.java:138)
com.ibm.io.async.ResultHandler.complete(ResultHandler.java:204)
com.ibm.io.async.ResultHandler.runEventProcessingLoop(ResultHandler.java:775)
com.ibm.io.async.ResultHandler$2.run(ResultHandler.java:905)
com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1604)

Any idea on how to fix it?

Thanks!