An unexpected ErrorOccurredinReport Processing.System.UnauthorizedAccessException: Access to thePath 'C:\Windows\TEMP\expression_host_.dll' is denied

Question

It is a .NET web application and it is running for more than 7 years without issues. All of the sudden, while bulking printing it gives the below error.Basically, it exports 1000 plus reports in to separate PDF and saves in the folder. Out of 1000 reports it only fails to generate 5 or 6 reports. All other reports prints well. It happens randomly and also occasionally. What could be the possible reasons?

I also tried these below solutions, nothing works

1. Assigned full rights for IIS_IUSRS and IUSR of vitrual directory in IIS.
2. Assigned full rights for IIS_IUSRS and IUSR of Temp folder.
3. Changed pipeline mode for app pool from Integrated to Classic mode.
4. Tried with different App pool identities.

Why does it loses access to TEMP folder?

Error:

An unexpected error occurred in Report Processing. ---> System.UnauthorizedAccessException: Access to the path 'C:\Windows\TEMP\expression_host_55d5319b1c4846ed963bf635fd27599b.dll' is denied.



Exception: The definition of the report 'reportname.rdlc' is invalid.
Exception string: Microsoft.Reporting.WebForms.LocalProcessingException: An error occurred during local report processing. ---> Microsoft.Reporting.DefinitionInvalidException: The definition of the report 'reportname.rdlc' is invalid. ---> Microsoft.ReportingServices.ReportProcessing.ReportProcessingException: An unexpected error occurred in Report Processing. ---> System.UnauthorizedAccessException: Access to the path 'C:\Windows\TEMP\expression_host_55d5319b1c4846ed963bf635fd27599b.dll' is denied.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.InternalDelete(String path, Boolean checkHost)
   at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.InternalCompile(AppDomain compilationTempAppDomain, Boolean refusePermissions)
   at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.<>c__DisplayClass2.<Compile>b__0()
   at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.<>c__DisplayClass1.<Run>b__0(Object state)
   at System.Security.SecurityContext.Run(SecurityContext securityContext, ContextCallback callback, Object state)
   at Microsoft.ReportingServices.Diagnostics.RevertImpersonationContext.Run(ContextBody callback)
   at Microsoft.ReportingServices.RdlExpressions.ExprHostCompiler.Compile(IExpressionHostAssemblyHolder expressionHostAssemblyHolder, AppDomain compilationTempAppDomain, Boolean refusePermissions, PublishingVersioning versioning)
   at Microsoft.ReportingServices.ReportPublishing.ReportPublishing.Phase3(ParameterInfoCollection& parameters, Dictionary`2& groupingExprCountAtScope)
   at Microsoft.ReportingServices.ReportPublishing.ReportPublishing.InternalCreateIntermediateFormat(Stream definitionStream, String& description, String& language, ParameterInfoCollection& parameters, DataSourceInfoCollection& dataSources, DataSetInfoCollection& sharedDataSetReferences, UserLocationFlags& userReferenceLocation, ArrayList& dataSetsName, Boolean& hasExternalImages, Boolean& hasHyperlinks, Byte[]& dataSetsHash)
   at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.CompileOdpReport(PublishingContext reportPublishingContext, IDataProtection dataProtection, PublishingErrorContext errorContext, String& reportDescription, String& reportLanguage, ParameterInfoCollection& parameters, DataSourceInfoCollection& dataSources, DataSetInfoCollection& sharedDataSetReferences, UserLocationFlags& userReferenceLocation, ArrayList& dataSetsName, Boolean& hasExternalImages, Boolean& hasHyperlinks, Byte[]& dataSetsHash)
   at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.CreateIntermediateFormat(PublishingContext reportPublishingContext, IDataProtection dataProtection)
   --- End of inner exception stack trace ---
   at Microsoft.ReportingServices.ReportProcessing.ReportProcessing.CreateIntermediateFormat(PublishingContext reportPublishingContext, IDataProtection dataProtection)
   at Microsoft.Reporting.ReportCompiler.CompileReport(ICatalogItemContext context, Byte[] reportDefinition, Boolean generateExpressionHostWithRefusedPermissions, ControlSnapshot& snapshot)
   --- End of inner exception stack trace ---
   at Microsoft.Reporting.ReportCompiler.CompileReport(ICatalogItemContext context, Byte[] reportDefinition, Boolean generateExpressionHostWithRefusedPermissions, ControlSnapshot& snapshot)
   at Microsoft.Reporting.LocalService.GetCompiledReport(PreviewItemContext itemContext, Boolean rebuild, ControlSnapshot& snapshot)
   at Microsoft.Reporting.LocalService.CompileReport()
   at Microsoft.Reporting.WebForms.LocalReport.EnsureExecutionSession()
   --- End of inner exception stack trace ---
   at Microsoft.Reporting.WebForms.LocalReport.EnsureExecutionSession()
   at Microsoft.Reporting.WebForms.LocalReport.InternalRender(String format, Boolean allowInternalRenderers, String deviceInfo, PageCountMode pageCountMode, CreateAndRegisterStream createStreamCallback, Warning[]& warnings)
   at Microsoft.Reporting.WebForms.LocalReport.InternalRender(String format, Boolean allowInternalRenderers, String deviceInfo, PageCountMode pageCountMode, String& mimeType, String& encoding, String& fileNameExtension, String[]& streams, Warning[]& warnings)