Error importing xliff translation

When I import a xliff translation file I get an error. Is there anybody who can tell me what might be wrong based on the error message below?

<?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>auth0|59ae53a1d1a25c6b807da557</UserId>
<HardwareId>R25WM-HVEU3-FU11A-U3VVT-1LH1S</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.CreateDocument(transunit translationUnit)
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.LoadXliff(IList&lt;ITranslationUnit&gt; items, string fileName)
at void Articulate.Globalization.TranslationProvider.StartProvider()
at Articulate.Globalization.TranslationProvider()+(object _, EventArgs __) =&gt; { } [0]
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>