Issue when importing XLF translated file

Hi,

I get each time an error when I try to import my translated XLF file.
He starts the import and like two chapters he translates and then he gives an error report. It says "An item with the same key has already been added."

I tried making a new XLF export, made translation, import again, always the same message.

Can anyone help me out, costed me already 2 days of trying and because it is a very huge E-learning file...?  Thanks guys, any suggestion is welcome.

Details of the error report: 

<?xml version="1.0" encoding="utf-16"?>
<ErrorReport xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
<UserId>aid|91f484b6-7f96-413c-9a6a-b02f2752355c</UserId>
<HardwareId>9T4K9-0QG2H-Q3FUX-UAUU9-V2U6D</HardwareId>
<Message>An item with the same key has already been added.</Message>
<StackTrace> at void System.Collections.Generic.Dictionary&lt;TKey, TValue&gt;.Insert(TKey key, TValue value, bool add)
at Dictionary&lt;TKey, TElement&gt; System.Linq.Enumerable.ToDictionary&lt;TSource, TKey, TElement&gt;(IEnumerable&lt;TSource&gt; source, Func&lt;TSource, TKey&gt; keySelector, Func&lt;TSource, TElement&gt; elementSelector, IEqualityComparer&lt;TKey&gt; comparer)
at IList&lt;XElement&gt; Articulate.Globalization.Internal.Xliff.V1_2.XliffItemsParser.GetBlocks(IEnumerable&lt;object&gt; source)
at XDocument Articulate.Globalization.Internal.Xliff.V1_2.DocumentStateTranslationUnitBuilder.a(transunit A_0)
at bool Articulate.Globalization.Internal.Xliff.V1_2.DocumentStateTranslationUnitBuilder.Apply(ITranslationUnit projectTranslationUnit, transunit translationUnit)
at bool Articulate.Globalization.Internal.Xliff.V1_2.TranslationUnitFactory.Apply(transunit translationUnit, ITranslationLoader translationLoader, Func&lt;string, ITranslationUnit&gt; projectTranslationUnitLookup)
at void Articulate.Globalization.Internal.Xliff.V1_2.XliffBuilder.Apply(string fileName, ITranslationLoader translationLoader, IEnumerable&lt;ITranslationUnit&gt; units)
at bool Articulate.Globalization.TranslationProvider.a(IList&lt;ITranslationUnit&gt; A_0, string A_1)
at void Articulate.Globalization.TranslationProvider.b()
at void Articulate.Globalization.TranslationProvider.b(object A_0, EventArgs A_1)
at void Articulate.Globalization.TranslationImportResult.OnShown(EventArgs e)
at void System.Windows.Forms.Form.CallShownEvent()
at void System.Windows.Forms.Control.InvokeMarshaledCallbackDo(ThreadMethodEntry tme)
at void System.Windows.Forms.Control.InvokeMarshaledCallbackHelper(object obj)
at void System.Windows.Forms.Control.InvokeMarshaledCallback(ThreadMethodEntry tme)
at void System.Windows.Forms.Control.InvokeMarshaledCallbacks()</StackTrace>
</ErrorReport>