RFC_ERROR_SYSTEM_FAILURE in business connector 47

Hi,

I am getting the following RFc exceptions in BC server when we invoke the service pub.sap.client:invoke fail as a flow step in Idoc_Status_Add(this service is calling a function module in sap namely ZYBC_IDOC_STATUS_ADD_FROM_BC which Adds status to Idoc (from Business Connector).But no trace of failures are recorded in sap side
except 1: rfc_failure in BC trace files under monitoring.I need to know the root cause of these errors as the same services have run finely later and IDOCs were also processed successfully without any problem.

com.sap.mw.jco.JCO$Exception: (104) RFC_ERROR_SYSTEM_FAILURE: See RFC trace file or SAP system log for more details
at com.sap.mw.jco.rfc.MiddlewareRFC$Client.nativeExecute(Native Method)
at com.sap.mw.jco.rfc.MiddlewareRFC$Client.execute(MiddlewareRFC.java:1217)
at com.sap.mw.jco.JCO$Client.execute(JCO.java:3684)
at com.sap.mw.jco.JCO$Client.execute(JCO.java:3129)
at com.wm.pkg.sap.rfc.SAPSession.invoke(SAPSession.java:437)
at pub.sap.client.invoke(client.java:297)
at java.lang.reflect.Method.invoke(Native Method)
at com.wm.app.b2b.server.JavaService.baseInvoke(JavaService.java:281)
at com.wm.app.b2b.server.ServiceManager.invoke(ServiceManager.java:709)
at com.wm.app.b2b.server.BaseService.invoke(BaseService.java:140)
at com.wm.lang.flow.FlowInvoke.invoke(FlowInvoke.java:292)
at com.wm.lang.flow.FlowState.invokeNode(FlowState.java:559)
at com.wm.lang.flow.FlowState.step(FlowState.java:430)
at com.wm.lang.flow.FlowState.invoke(FlowState.java:400)
at com.wm.app.b2b.server.FlowSvcImpl.baseInvoke(FlowSvcImpl.java:1786)
at com.wm.app.b2b.server.ServiceManager.invoke(ServiceManager.java:709)
at com.wm.app.b2b.server.BaseService.invoke(BaseService.java:140)
at com.wm.lang.flow.FlowInvoke.invoke(FlowInvoke.java:292)
at com.wm.lang.flow.FlowState.invokeNode(FlowState.java:559)
at com.wm.lang.flow.FlowState.step(FlowState.java:430)
at com.wm.lang.flow.FlowState.invoke(FlowState.java:400)
at com.wm.app.b2b.server.FlowSvcImpl.baseInvoke(FlowSvcImpl.java:1786)
at com.wm.app.b2b.server.ServiceManager.invoke(ServiceManager.java:709)
at com.wm.app.b2b.server.ServiceManager.invoke(ServiceManager.java:496)
at wm.server.net.EmailTransaction$RunService.write(EmailTransaction.java:1375)
at wm.server.net.EmailTransaction$RunService.run(EmailTransaction.java:1218)
at com.wm.util.pool.PooledThread.run(C:/NT/Perforce/basis/4.1.0-terra/module/core/source/com/wm/util/pool/PooledThread.java:103)
at java.lang.Thread.run(Unknown Source)

could anyone throw light on how this kind of error can be resolved and why it occured?
Thanks.