"la référence d'objet n'est pas définie à une instance d'un objet"

I get this message when I try to save my sdlxliff file to  Word. I'm using Studio 2019 with Word 2013 on Windows 2010 (PC). I saved the same file yesterday with no problems. I can't do screen shot of the error message so here what I have when I save it.

Thanks in advance

<SDLErrorDetails time="18/09/2020 08:06:13">
<ErrorMessage>Échec de l'enregistrement du contenu cible : La référence d'objet n'est pas définie à une instance d'un objet.</ErrorMessage>
<Exception>
<Type>System.NullReferenceException, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</Type>
<HelpLink />
<Source>Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word_2</Source>
<HResult>-2147467261</HResult>
<StackTrace><![CDATA[ à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Consumers.Writer.FootnoteOrEndnoteReferencePlaceholderConsumer.ProcessUpperPlaceholder(IPlaceholderTag placeholder)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Consumers.Writer.FootnoteOrEndnoteReferencePlaceholderConsumer.Consume(IPlaceholderTag placeholder)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Routes.Writer.PlaceholderFoundRoute.Handle(PlaceholderFound placeholderFound)
à lambda_method(Closure , IMessage )
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.MarkupDataEventsPublisherService.VisitPlaceholderTag(IPlaceholderTag tag)
à Sdl.FileTypeSupport.Framework.Bilingual.PlaceholderTag.AcceptVisitor(IMarkupDataVisitor visitor)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.MarkupDataEventsPublisherService.PublishEventsFrom(IEnumerable`1 container)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Routes.Writer.SegmentFoundRoute.Handle(SegmentFound segmentFound)
à lambda_method(Closure , IMessage )
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.MarkupDataEventsPublisherService.VisitSegment(ISegment segment)
à Sdl.FileTypeSupport.Framework.Bilingual.Segment.AcceptVisitor(IMarkupDataVisitor visitor)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.MarkupDataEventsPublisherService.PublishEventsFrom(IEnumerable`1 container)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.ParagraphUnitEventsPublisherService.PublishNonEmptyActiveParagraph(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.ParagraphUnitEventsPublisherService.PublishParagraphUnitAndNonEmptyActiveParagraph(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Services.ReplaceTargetContentService.PublishParagraphUnitAndUpdateReplacedContentPosition()
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Routes.Writer.ReplaceTargetContentRoute.Handle(Entity entity)
à lambda_method(Closure , IMessage )
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Infrastructure.Dispatcher.Publish(IMessage message)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Publish(Entity parsedEntity)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Services.ParserService.Parse()
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Core.Parser.DocumentParser.Parse()
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Writer.DocumentWriter.Process()
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Writer.DocxWriter.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Filters.MicrosoftOffice.Word.Processors.HandleActionByTagTypeProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.BilingualApi.AbstractBilingualContentProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Filters.Processors.CopySourceToEmptyTargetProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Bilingual.WhitespaceBetweenSegmentsBilingualProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.BilingualApi.AbstractBilingualContentProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.GenerationBilingualContentLocator.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.AbstractBilingualProcessorContainer.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.FileGenerator.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.AbstractBilingualProcessorContainer.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.BilingualApi.AbstractBilingualContentProcessor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.LocationMarkerLocator.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.AbstractBilingualProcessorContainer.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ProcessParagraphUnit(IParagraphUnit paragraphUnit)
à Sdl.FileTypeSupport.Bilingual.Tmfc.TmfcReaderImpl.vv_Visit(TmfcReaderImpl* , FrameworkParagraphContainerField* field)
à FrameworkParagraphContainerField.vv_AcceptFrameworkVisitor(FrameworkParagraphContainerField* , FrameworkFieldVisitor* visitor)
à Sdl.FileTypeSupport.Bilingual.Tmfc.TmfcReaderImpl.vv_VisitStartEndField(TmfcReaderImpl* , StartEndField* startEnd)
à Sdl.FileTypeSupport.Bilingual.Tmfc.TmfcReaderImpl.b_VisitNext(TmfcReaderImpl* )
à Sdl.FileTypeSupport.Bilingual.Tmfc.TmfcReader.ParseNext()
à Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ParseNext()
à Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.ParseNext()
à Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.Parse()
à Sdl.TranslationStudio.Editor.TranslationEditor.SaveMonolingualAsJobRequest.Execute(IJobExecutionContext context)
à Sdl.Desktop.Platform.Implementation.Services.Job.<_worker_DoWork>b__47_0()
à Sdl.Desktop.Logger.Log.Resources(Object message, Action action)
à Sdl.Desktop.Platform.Implementation.Services.Job._worker_DoWork(Object sender, DoWorkEventArgs e)
à System.ComponentModel.BackgroundWorker.OnDoWork(DoWorkEventArgs e)
à System.ComponentModel.BackgroundWorker.WorkerThreadStart(Object argument)]]></StackTrace>
</Exception>
<Environment>
<ProductName>SDL Trados Studio</ProductName>
<ProductVersion>15.0.0.0</ProductVersion>
<EntryAssemblyFileVersion>15.2.0.1041</EntryAssemblyFileVersion>
<OperatingSystem>Microsoft Windows 10 Professionnel</OperatingSystem>
<ServicePack>NULL</ServicePack>
<OperatingSystemLanguage>1036</OperatingSystemLanguage>
<CodePage>1252</CodePage>
<LoggedOnUser>THINKPAD\Martha</LoggedOnUser>
<DotNetFrameWork>4.0.30319.42000</DotNetFrameWork>
<ComputerName>THINKPAD</ComputerName>
<ConnectedToNetwork>True</ConnectedToNetwork>
<PhysicalMemory>16639064 MB</PhysicalMemory>
</Environment>
</SDLErrorDetails>