CSV Import for Subtasks with Epics is failing for user in 8.13.1 whereas the same CSV file successfully imports in 8.5.1

2021-01-18 15:45:48,665 INFO - Importer started!
2021-01-18 15:45:48,666 INFO - Engine is running in Import mode
2021-01-18 15:45:48,678 INFO - All issues will be imported to project: TEST (TEST)
2021-01-18 15:45:48,698 INFO - Creating issue: [externalId='autoid-3352800770143679451', summary='Summary 1']
2021-01-18 15:45:48,888 ERROR - Fatal error during import
java.lang.IllegalArgumentException: Sub-Task Issue cannot be null.
	at com.atlassian.jira.config.DefaultSubTaskManager.createSubTaskIssueLink(DefaultSubTaskManager.java:435)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at com.atlassian.plugin.util.ContextClassLoaderSettingInvocationHandler.invoke(ContextClassLoaderSettingInvocationHandler.java:26)
	at com.sun.proxy.$Proxy516.createSubTaskIssueLink(Unknown Source)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:343)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.doInvoke(ServiceInvoker.java:56)
	at org.eclipse.gemini.blueprint.service.importer.support.internal.aop.ServiceInvoker.invoke(ServiceInvoker.java:60)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invokeUnprivileged(ServiceTCCLInterceptor.java:70)
	at org.eclipse.gemini.blueprint.service.util.internal.aop.ServiceTCCLInterceptor.invoke(ServiceTCCLInterceptor.java:53)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.eclipse.gemini.blueprint.service.importer.support.LocalBundleContextAdvice.invoke(LocalBundleContextAdvice.java:57)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.doProceed(DelegatingIntroductionInterceptor.java:136)
	at org.springframework.aop.support.DelegatingIntroductionInterceptor.invoke(DelegatingIntroductionInterceptor.java:124)
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:185)
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
	at com.sun.proxy.$Proxy7048.createSubTaskIssueLink(Unknown Source)
	at com.atlassian.jira.plugins.importer.compatibility.CompatibilityUtil71.createSubTaskIssueLink(CompatibilityUtil71.java:237)
	at com.atlassian.jira.plugins.importer.compatibility.CompatibilityBridgeUtils.createSubTaskIssueLink(CompatibilityBridgeUtils.java:118)
	at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.createSubTaskLink(BulkCreateDataImporter.java:325)
	at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.doImportSubtasks(BulkCreateDataImporter.java:297)
	at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.runImporterEngine(BulkCreateDataImporter.java:174)
	at com.atlassian.jira.plugins.importer.imports.bulkcreate.engine.BulkCreateDataImporter.doImport(BulkCreateDataImporter.java:147)
	at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:26)
	at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:15)
	at com.atlassian.jira.task.TaskManagerImpl$TaskCallableDecorator.call(TaskManagerImpl.java:533)
	at com.atlassian.jira.task.TaskManagerImpl$TaskCallableDecorator.call(TaskManagerImpl.java:491)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
	at com.atlassian.jira.task.ForkedThreadExecutor$ForkedRunnableDecorator.run(ForkedThreadExecutor.java:216)
	at java.lang.Thread.run(Thread.java:748)