Files are going into recovery at the "Rebuild Translation" step in TMS.  This may be specifically for one target language (potentially, one single user within that languages group).  The Recovery error message is like the below:

XmlException : An error occurred while parsing EntityName. Line 37, position 586. : System.Xml : at System.Xml.XmlTextReaderImpl.Throw(Exception e) at System.Xml.XmlTextReaderImpl.Throw(String res, String arg) at System.Xml.XmlTextReaderImpl.ParseEntityName() at System.Xml.XmlTextReaderImpl.ParseEntityReference() at System.Xml.XmlTextReaderImpl.Read() at Sdl.FileTypeSupport.Bilingual.SdlXliff.WhitespacePreservingXmlTextReader.Read() at System.Xml.XmlLoader.LoadNode(Boolean skipOverWhitespace) at System.Xml.XmlLoader.ReadCurrentNode(XmlDocument doc, XmlReader reader) at System.Xml.XmlDocument.ReadNode(XmlReader reader) at Sdl.FileTypeSupport.Bilingual.SdlXliff.SdlXliffFeeder.GetXmlElement(XmlReader xmlReader) at Sdl.FileTypeSupport.Bilingual.SdlXliff.SdlXliffFeeder.<ContinueScanning>b__10(ISdlXliffStreamContentHandler handler) at System.Collections.Generic.List`1.ForEach(Action`1 action) at Sdl.FileTypeSupport.Bilingual.SdlXliff.SdlXliffFeeder.ContinueScanning() at Sdl.FileTypeSupport.Bilingual.SdlXliff.GenericStreamReader.ProcessStream(String xliffInputFilePath) at Sdl.FileTypeSupport.Bilingual.SdlXliff.XliffFileReader.InitializeDocumentProperties() at Sdl.FileTypeSupport.Bilingual.SdlXliff.XliffFileReader.BeginParsing() at Sdl.FileTypeSupport.Bilingual.SdlXliff.XliffFileReader.ParseNext() at Sdl.FileTypeSupport.Framework.Integration.FileExtractor.ParseNext() at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.ParseNext() at Sdl.FileTypeSupport.Framework.Integration.MultiFileConverter.Parse() at Sdl.Tms.Ppt.PptBaseCore.DoEntireUpdate(PreprocessingWorkItem taskItem) at Sdl.Tms.Ppt.PptBaseCore.RebuildAll(Int32 taskId, Boolean checkFormatPainting) at Sdl.Tms.Workflow.PreProcess.RebuildFile.Execute() at Sdl.Tms.MessageProcessing.WorkerRequestProcessor.ExecuteMessage()

There are two possible fixes depending on the root cause:

1.) Invalid XML.  Open the target file in a text editor such as NotePad++, which will help you identify the location of the offending entity.  Translators can then rectify this translation in the bilingual file.

2.) A problematic User Name.  This is fixed in versions of Studio newer than Studio 2015 SR3.  The short term fix is to contact the user in question and ask them to change their username, removing such characters.  They can then download a fresh sdlxliff file, applying their translations to it and re-uploading.  The task should then submit without issue.

There are two possibilities:

1.) The XML itself is invalid, for example featuring an unencoded "&", rather than "&amp;"

2.) Alternatively, it could be due to the Username of the translator, which is set in Studio under File > Setup > Users > TM User ID.

This username is likely to have an ampersand (&) in it, or another entity which is not xml-encoded. When TMS then attempts to open this xliff, it is classed as invalid XML