ObjectNotFoundExceptions with jBPM timers in SOA-P 5.1

Issue

We are using jBPM processes with timers inside the SOA platform, and noticed that the server.log file is full of errors that look like the following:

2011-05-13 11:41:58,220 ERROR [org.jboss.resource.adapter.jms.inflow.JmsServerSession] (WorkManager(2)-24) Unexpected error delivering message delegator->JBossMessage[5346159532965897]:PERSISTENT, deliveryId=9
org.jbpm.JbpmException: could not process message delegator->JBossMessage[5346159532965897]:PERSISTENT, deliveryId=9
     at org.jboss.soa.esb.services.jbpm.integration.command.AbstractMessageListener.onMessage(AbstractMessageListener.java:126)
     at org.jboss.soa.esb.services.jbpm.integration.command.JobListener.onMessage(JobListener.java:16)
     at sun.reflect.GeneratedMethodAccessor474.invoke(Unknown Source)
     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
     at java.lang.reflect.Method.invoke(Method.java:597)
     at org.jboss.internal.soa.esb.dependencies.JCAInflowAdapter$1.invoke(JCAInflowAdapter.java:276)
     at org.jboss.soa.esb.listeners.jca.EndpointProxy.delivery(EndpointProxy.java:258)
     at org.jboss.soa.esb.listeners.jca.EndpointProxy.invoke(EndpointProxy.java:150)
     at $Proxy309.onMessage(Unknown Source)
     at org.jboss.resource.adapter.jms.inflow.JmsServerSession.onMessage(JmsServerSession.java:179)
     at org.jboss.jms.client.container.ClientConsumer.callOnMessageStatic(ClientConsumer.java:160)
     at org.jboss.jms.client.container.SessionAspect.handleRun(SessionAspect.java:831)
     at org.jboss.aop.advice.org.jboss.jms.client.container.SessionAspect_z_handleRun_10685006.invoke(SessionAspect_z_handleRun_10685006.java)
     at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
     at org.jboss.jms.client.container.ClosedInterceptor.invoke(ClosedInterceptor.java:172)
     at org.jboss.aop.advice.PerInstanceInterceptor.invoke(PerInstanceInterceptor.java:86)
     at org.jboss.aop.joinpoint.MethodInvocation.invokeNext(MethodInvocation.java:102)
     at org.jboss.jms.client.delegate.ClientSessionDelegate.run(ClientSessionDelegate.java)
     at org.jboss.jms.client.JBossSession.run(JBossSession.java:199)
     at org.jboss.resource.adapter.jms.inflow.JmsServerSession.run(JmsServerSession.java:236)
     at org.jboss.resource.work.WorkWrapper.execute(WorkWrapper.java:205)
     at org.jboss.util.threadpool.BasicTaskWrapper.run(BasicTaskWrapper.java:260)
     at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
     at java.lang.Thread.run(Thread.java:662)
Caused by: org.hibernate.ObjectNotFoundException: No row with the given identifier exists: [org.jbpm.job.Timer#1109]
     at org.hibernate.impl.SessionFactoryImpl$2.handleEntityNotFound(SessionFactoryImpl.java:418)
     at org.hibernate.proxy.AbstractLazyInitializer.checkTargetState(AbstractLazyInitializer.java:154)
     at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:143)
     at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174)
     at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
     at org.jbpm.job.Timer_$$_javassist_68.getProcessInstance(Timer_$$_javassist_68.java)
     at org.jboss.soa.esb.services.jbpm.integration.job.ExecuteTimerCommand.execute(ExecuteTimerCommand.java:68)
     at org.jboss.soa.esb.services.jbpm.integration.command.AbstractMessageListener.onMessage(AbstractMessageListener.java:66)
     ... 24 more