You are currently working on UAT 

Object reference not set to an instance of an object - Studio 2019

Attached is my error message. How can I know which PPT slide or Excel Sheet is creating the problem?

<SDLErrorDetails time="2019-01-17 1:19:21 PM">
<ErrorMessage>Object reference not set to an instance of an object.</ErrorMessage>
<Exception>
<Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<HelpLink />
<Source>Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel_2</Source>
<HResult>-2147467261</HResult>
<StackTrace><![CDATA[ at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Charts.StoreTitleTextRoute.Handle(Entity entity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Routes.DispatchRoute.Dispatch(Entity entity)
at lambda_method(Closure , IMessage )
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Publish(Entity parsedEntity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Parse()
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Parser.DispatchingParserService.Process(Func`1 inputStreamFactory, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Charts.ChartParser.Parse(String chartFilePath)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Charts.ChartReferenceRoute.Handle(Entity entity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Routes.DispatchRoute.Dispatch(Entity entity)
at lambda_method(Closure , IMessage )
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Publish(Entity parsedEntity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Parse()
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Parser.DispatchingParserService.Process(Func`1 inputStreamFactory, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Drawings.DrawingParser.Parse(String drawingFilePath)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Drawings.DrawingReferenceRoute.Handle(Entity entity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Routes.DispatchRoute.Dispatch(Entity entity)
at lambda_method(Closure , IMessage )
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Publish(Entity parsedEntity)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Parse()
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Parser.DispatchingParserService.Process(Func`1 inputStreamFactory, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Archive.WorksheetsParser.ProcessSheetContent(IDispatcherConfiguration dispatcherConfiguration, SheetReference sheetReference)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Archive.WorksheetsParser.<>c__DisplayClass6_0.<Process>b__0(SheetReference sheetReference)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Context.ExcelParserContext.ForEachSheetReference(Action`1 action)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Archive.WorksheetsParser.Process(IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.Parser.Archive.ArchiveParser.Parse(String archivePath, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.XlsxParser.ProcessArchive()
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Excel.XlsxParser.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.SubContentExtractor.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.FileExtractor.PublisherProcessSubContent(Object sender, ProcessSubContentEventArgs args)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.PptxParser.PublishContent(String subContentFileTypeDefinitionId, Stream subContentStream)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.EmbeddedFiles.EmbeddedFileProcessor.PublishEmbeddedContent(String embeddedFilePath, String subContentFileTypeDefinitionId)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.EmbeddedFiles.EmbeddedFileProcessor.Process(String embeddedFilePath, String relativeEmbeddedFilePath, String subContentFileTypeDefinitionId)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Charts.ChartProcessor.ProcessExternalData(Chart chart)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Charts.ChartProcessor.ProcessChart(Chart chart, SlideContentVisitor visitor)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Drawings.GraphicFrameProcessor.Process(GraphicFrame graphicFrame, SlideContentVisitor visitor)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Drawings.GraphicFrame.AcceptVisitor(SlideContentVisitor visitor)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Slides.ProcessSlideRoute.Handle(PostProcessSlide postProcessSlide)
at lambda_method(Closure , IMessage )
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Slides.SlideParser.PublishMessage(IMessage message, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Slides.SlideParser.ProcessSlide(IDispatcherConfiguration dispatcherConfiguration, SlideReference slideReference)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Slides.SlideParser.<>c__DisplayClass7_0.<Process>b__0(SlideReference slideReference)
at System.Collections.Generic.List`1.ForEach(Action`1 action)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Slides.SlideParser.Process(IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.Parser.Archive.ArchiveParser.Parse(String extractedArchivePath, IDispatcherConfiguration dispatcherConfiguration)
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.PptxParser.ProcessArchive()
at Sdl.FileTypeSupport.Filters.MicrosoftOffice.PowerPoint.PptxParser.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.ParseNext()
at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.Parse()
at Sdl.ProjectApi.AutomaticTasks.Conversion.ConversionTask.ProcessFile(IExecutingTaskFile executingTaskFile)
at Sdl.ProjectApi.AutomaticTasks.AbstractFileLevelAutomaticTaskImplementation.Execute()]]></StackTrace>
</Exception>
<Environment>
<ProductName>SDL Trados Studio</ProductName>
<ProductVersion>15.0.0.0</ProductVersion>
<EntryAssemblyFileVersion>15.1.0.44109</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 8.1</OperatingSystem>
<ServicePack>NULL</ServicePack>
<OperatingSystemLanguage>1033</OperatingSystemLanguage>
<CodePage>1252</CodePage>
<LoggedOnUser>PIYUSH-PC\Pascal</LoggedOnUser>
<DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
<ComputerName>PIYUSH-PC</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>8298520 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>