Unable to cast object of type '?.?' to type '?.?'

We get an error when we run ExecuteWithRegions with a template where we test on the contens of a field - is it empty or not. This test works fine for all string characters, but if we place a bracket in the text we want to merge, then the code fails with the following error 8beacuse of the empty or not test):
The error is: “Unable to cast object of type ‘❾.⡢’ to type ‘❾.➈’.”
The below small example can reconstruct this problem - Sourcecode + template also attached.
If you change the code line:

drMedie["navn"] = "Publicitas (service intern";

to:

drMedie["navn"] = "Publicitas s(ervice intern";

the test works fine. So our theory is that it must be something with the placement of the bracket that has influense on Aspose’s field type definition. We tried forcing a string conversion by using the * lower option, but that did not help.
We use Aspose.Words.dll vers. 9.1.0.0.
C# example:

namespace AsposeMergeRegionsError
{
    class Program
    {
        static void Main(string[] args)
        {
            var template = new FileStream("template/template.dot", FileMode.Open, FileAccess.ReadWrite);
            var document = new Document(template);
            try
            {
                document.MailMerge.ExecuteWithRegions(GetTestDataTable());
                document.Save("template/mergedfile.doc", SaveFormat.Doc);
                Console.WriteLine("ExecuteWithRegions completed");
            }
            catch (InvalidOperationException e)
            {
                Console.WriteLine("ExecuteWithRegions failed: " + e.Message);
            }
        }
        static DataSet GetTestDataTable()
        {
            var ds = new DataSet("testdataset");
            var dtMedie = new DataTable("mediebureau");
            dtMedie.Columns.Add("navn", Type.GetType("System.String"));
            var drMedie = dtMedie.NewRow();
            drMedie["navn"] = "Publicitas (service intern";
            dtMedie.Rows.Add(drMedie);
            ds.Tables.Add(dtMedie);
            return ds;
        }
    }
}

Word example:
{ MERGEFIELD TableStart:mediebureau * MERGEFORMAT }
{ IF «navn» <> “” "Navn: " “” }
{ MERGEFIELD TableEnd:mediebureau * MERGEFORMAT }

Hi
Thanks for your request. I cannot reproduce the problem on my side. I use the latest version of Aspose.Words for testing. You can download it from here:
https://releases.aspose.com/words/net
Best regards,