The indexes cannot be merged because they divide the text of documents into terms differently. The index 'other-index' differs from the current index in: StopWordDictionary.
[.NET System.InvalidOperationException]
   at .(IndexRepository , MergeOptions ,  , OperationType )

   at .(IndexRepository , MergeOptions ,  , OperationType )

   at .(Index , MergeOptions )

   at GroupDocs.Search.Index.Merge(Index index, MergeOptions options)

   at InvokeStub_Index.Merge(Object, Span`1)

   at System.Reflection.MethodBaseInvoker.InvokeWithFewArgs(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)