Error on createTextNode MATLAB 2015b XMLUtils

I write some data into a XML-file:

   [FileName,PathName] = uiputfile('*.xml','Select the XML file');
   if length(FileName) > 3
        completePath = [PathName FileName];
        % Create the DOM-Object
        docNode = com.mathworks.xml.XMLUtils.createDocument('docRootNode');
        docRootNode = docNode.getDocumentElement;
        docRootNode.setAttribute('version','2.0');
        mElement = docNode.createElement('Data1'); 
        docRootNode.appendChild(mElement)
        fields = fieldnames(struct1);
        for i = 1:numel(fields)
            thisElement = docNode.createElement(fields{i});
            thisElement.appendChild... 
            (docNode.createTextNode(struct1.(fields{i}))); %NO ERROR
            mElement.appendChild(thisElement);
        end
        rElement = docNode.createElement('Data2'); 
        docRootNode.appendChild(rElement)
        fields = fieldnames(struct2);
        for i = 1:numel(fields)
            thisElement = docNode.createElement(fields{i});
            thisElement.appendChild... 
            (docNode.createTextNode(struct2.(fields{i}))); %ERROR
            rElement.appendChild(thisElement); 
        end
    xmlwrite(completePath, docNode);
    end

Last week it worked without any problems, but since today I get this error in the line tagged with %ERROR running my code:

No method 'createTextNode' with matching signature found for class 'org.apache.xerces.dom.DocumentImpl'.

I did not find any solution searching the internet (a problem might be that I am no admin on my PC).
I also do not understand, why I got no error in the upper part (%NO ERROR)

My problem is solved with the support of MATLAB:
The only problem in my program was, that struct2 contained integer values.
struct1 contained only string-values, so there was no problem.
I use num2str to convert the numeric values now and have no problem anymore ;).