invalid callBlock error in flow designer

[Anjana Singh1]

I am processing file import sets by flow designer.

below error :-

Flow Designer: Operation(Data process from MID Server.66f54de487bc215010372fc8cebb3536.ForEach$1.item$3) failed with error: com.snc.process_flow.exception.ProcessAutomationException: invalid callBlock message = 0d64ead8876ced10e8a298a83cbb3599.ForEach$1.item$1=>>>ab8c72f01b206510c5e0a6cee54bcb1c.Flow-Transform imported data$1.If$1.waitForSubflowComplete./subflow. expected /start
at com.snc.process_flow.engine.ProcessEngine.callBlock(ProcessEngine.java:221)
at com.snc.process_flow.engine.CallBlockOperation.callBlock(CallBlockOperation.java:96)
at com.snc.process_flow.engine.CallBlockOperation.run(CallBlockOperation.java:69)
at com.snc.process_flow.engine.Operation.execute(Operation.java:208)
at com.snc.process_flow.engine.restricted_caller_access.ExecuteWithCallerAccessTracking.executeWithMetaStack(ExecuteWithCallerAccessTracking.java:21)
at com.snc.process_flow.engine.ProcessEngine.executeOps(ProcessEngine.java:560)
at com.snc.process_flow.engine.ProcessEngine.runInternal(ProcessEngine.java:466)
at com.snc.process_flow.engine.ProcessEngine.run(ProcessEngine.java:452)
at com.snc.process_flow.engine.ProcessAutomation.run(ProcessAutomation.java:79)
at com.snc.process_flow.engine.GlideProcessAutomation.runSync(GlideProcessAutomation.java:137)
at com.snc.process_flow.engine.GlideProcessAutomation.runWithDomain(GlideProcessAutomation.java:252)
at com.snc.process_flow.engine.GlideProcessAutomation.lambda$runAsUserSync$1(GlideProcessAutomation.java:219)
at com.snc.process_flow.engine.PFSessionClone.run(PFSessionClone.java:70)
at com.snc.process_flow.engine.GlidePFSession.runPlanAsUserSession(GlidePFSession.java:42)
at com.snc.process_flow.engine.GlideProcessAutomation.runAsUserSync(GlideProcessAutomation.java:217)
at com.snc.process_flow.engine.GlideProcessAutomation.messageFlow(GlideProcessAutomation.java:312)
at com.snc.process_flow.engine.GlideProcessAutomation.messageFlow(GlideProcessAutomation.java:277)
at com.snc.process_flow.engine.PFContext.processOnContextTermination(PFContext.java:443)
at com.snc.process_flow.engine.PFContext.savePlan(PFContext.java:352)
at com.snc.process_flow.engine.steps.ISavePlan.savePlan(ISavePlan.java:16)
at com.snc.process_flow.engine.GlideProcessAutomation.persistPlan(GlideProcessAutomation.java:869)

Issue is even if the flow and subflow completes importing data from data source and I can see in import set table the records are processed with no error, the subflow which processes the data also completes without any error still subflow send Fail result and at last full flow stops with above mentioned error.