Symbol > appears at the end of XML

Question

I have an XML document that serves for a program in Java save some values that will be read by another in C#. It’s not the best way to exchange values between languages (that’s what happened, but I accept alternative suggestions), but it works relatively well, the problem is that when I update XML values, sometimes (apparently randomly), at the end of the XML text appears the symbol ">", and I have no idea why, and this causes the following error:

[Fatal Error] test.xml:1:200: Content is not allowed in trailing section.

The error-free XML is as follows: (I idented XML for ease*)

<?xml version="1.0" encoding="ASCII" standalone="no"?>
    <Data>
        <v1>0</v1>
        <v2>0</v2>
        <v3>0</v3>
        <v4>60</v4>
        <avg>60</avg>
        <lvl1>70</lvl1>
        <lvl2>85</lvl2>
        <lvl3>100</lvl3>
        <lvl4>115</lvl4>
        <hRate>75</hRate>
    </Data>

Since what has the error stays like this:

<?xml version="1.0" encoding="ASCII" standalone="no"?>
    <Data>
        <v1>0</v1>
        <v2>0</v2>
        <v3>0</v3>
        <v4>60</v4>
        <avg>60</avg>
        <lvl1>70</lvl1>
        <lvl2>85</lvl2>
        <lvl3>100</lvl3>
        <lvl4>115</lvl4>
        <hRate>75</hRate>
    </Data>> //ERRO NESTA LINHA

The part of the code that updates XML is this:

    public static void UpdateValuesXML(XMLParametter... param)
{
    try {
        String tempDir = System.getProperty(property); //find windows temp folder
        DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
        DocumentBuilder builder = factory.newDocumentBuilder();
        Document doc = builder.parse(tempDir + fileName);

        for (int i = 0; i < param.length; i++) 
        {
            Node val = doc.getElementsByTagName(XMLValue(param[i].param)).item(0);
            val.setTextContent(Integer.toString(param[i].value));
        }

        TransformerFactory transformerFactory = TransformerFactory.newInstance();
        Transformer transformer = transformerFactory.newTransformer();
        DOMSource source = new DOMSource(doc);
        StreamResult result = new StreamResult(new File(tempDir + fileName));
        transformer.transform(source, result);

    } catch (Exception ex) {}
}