We could see the below entry in SMA exception during the agent run where it has failed with stale thread error. It is happening frequently and we are running the bix manually in the application. What could be the cause of this and do we have any fix for this issue??

Exception at 20180202T021903.114 GMT: com.pega.pegarules.pub.context.StaleThreadError: Thread has been recycled at com.pega.pegarules.session.internal.mgmt.base.ThreadData.validateUse(ThreadData.java:746) at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.validateUse(PRThreadImpl.java:156) at com.pega.pegarules.session.internal.mgmt.PRThreadImpl.setInferenceEngineEnabled(PRThreadImpl.java:944) at com.pega.pegarules.data.internal.access.ExtractImpl.runExtract(ExtractImpl.java:1662) at com.pega.pegarules.data.internal.access.ExtractImpl.run(ExtractImpl.java:1463) at com.pega.pegarules.session.internal.PRSessionProviderImpl.performTargetActionWithLock(PRSessionProviderImpl.java:1177) at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:926) at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:777) at com.pega.pegarules.data.internal.access.ExtractImpl.runEngineExtract(ExtractImpl.java:1447) at com.pega.pegarules.data.internal.access.DatabaseImpl.executeExtract(DatabaseImpl.java:6988) at com.pega.pegarules.session.internal.mgmt.Executable.executeExtract(Executable.java:8112) at com.pegarules.generated.activity.ra_action_runextract_7eb17a5ada24845605c3d982093ca8a6.step1_circum0(ra_action_runextract_7eb17a5ada24845605c3d982093ca8a6.java:169) at com.pegarules.generated.activity.ra_action_runextract_7eb17a5ada24845605c3d982093ca8a6.perform(ra_action_runextract_7eb17a5ada24845605c3d982093ca8a6.java:69) at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3375) at com.pega.pegarules.session.internal.mgmt.Executable.invokeActivity(Executable.java:10450) at com.pegarules.generated.activity.ra_action_runextractforecr_ec3712ecf578e08890d32479aa394ad0.step3_circum0(ra_action_runextractforecr_ec3712ecf578e08890d32479aa394ad0.java:332) at com.pegarules.generated.activity.ra_action_runextractforecr_ec3712ecf578e08890d32479aa394ad0.perform(ra_action_runextractforecr_ec3712ecf578e08890d32479aa394ad0.java:116) at com.pega.pegarules.session.internal.mgmt.Executable.doActivity(Executable.java:3375) at com.pega.pegarules.session.internal.async.agent.QueueProcessor.runActivity(QueueProcessor.java:719) at com.pega.pegarules.session.internal.async.agent.QueueProcessor.execute(QueueProcessor.java:600) at com.pega.pegarules.session.internal.async.BatchRequestorTask.run(BatchRequestorTask.java:885) at com.pega.pegarules.session.internal.PRSessionProviderImpl.performTargetActionWithLock(PRSessionProviderImpl.java:1177) at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:926) at com.pega.pegarules.session.internal.PRSessionProviderImpl.doWithRequestorLocked(PRSessionProviderImpl.java:825) at com.pega.pegarules.session.internal.async.BatchRequestorTask.run(BatchRequestorTask.java:618) at com.pega.pegarules.session.internal.async.Agent.queueBatchActivityForAgent(Agent.java:1505) at com.pega.pegarules.session.internal.async.Agent.queueBatchActivityForAgent(Agent.java:1294) at com.pega.pegarules.session.internal.async.AgentQueue.run(AgentQueue.java:769) at com.pega.pegarules.session.internal.async.Agent.runAgentTask(Agent.java:937) at com.pega.pegarules.session.internal.engineinterface.etier.impl.AsyncServant.processAsyncTask(AsyncServant.java:220) at com.pega.pegarules.session.internal.engineinterface.etier.impl.AsyncServant.invoke(AsyncServant.java:166) at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl._invokeEngine_privact(EngineImpl.java:315) at com.pega.pegarules.session.internal.engineinterface.etier.impl.EngineImpl.invokeEngine(EngineImpl.java:263) at com.pega.pegarules.session.internal.engineinterface.etier.ejb.EngineBean.invokeEngine(EngineBean.java:225) at sun.reflect.GeneratedMethodAccessor95.invoke(Unknown Source) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:56) at java.lang.reflect.Method.invoke(Method.java:620) at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethod(PRBootstrap.java:338) at com.pega.pegarules.internal.bootstrap.PRBootstrap.invokeMethodPropagatingThrowable(PRBootstrap.java:379) at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingThrowable(AppServerBridgeToPega.java:216) at com.pega.pegarules.boot.internal.extbridge.AppServerBridgeToPega.invokeMethodPropagatingException(AppServerBridgeToPega.java:238) at com.pega.pegarules.internal.etier.ejb.EngineBeanBoot.invokeEngine(EngineBeanBoot.java:168) at com.pega.pegarules.internal.etier.interfaces.EJSLocalStatelessEngineBMT_f2439d86.invokeEngine(Unknown Source) at com.pega.pegarules.session.internal.engineinterface.etier.mdb.PRAsync.processRequest(PRAsync.java:155) at com.pega.pegarules.session.internal.engineinterface.etier.asynchbeans.AsyncTask.run(AsyncTask.java:64) at com.pega.pegarules.session.internal.engineinterface.etier.asynchbeans.RunnableWrapper.run(RunnableWrapper.java:71) at com.ibm.ws.asynchbeans.J2EEContext$RunProxy.run(J2EEContext.java:269) at java.security.AccessController.doPrivileged(AccessController.java:277) at com.ibm.ws.asynchbeans.J2EEContext.run(J2EEContext.java:795) at com.ibm.ws.asynchbeans.WorkWithExecutionContextImpl.go(WorkWithExecutionContextImpl.java:222) at com.ibm.ws.asynchbeans.ABWorkItemImpl.run(ABWorkItemImpl.java:206) at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java:1864)