Word to HTML fields in header and footer - docx4j

Question

I'm using docx4j to convert a Word template to several HTML files, one per chapter.
The Word template has several custom properties mapped by several fields (DOCPROPERTY ...) represented as both simple and complex fields. I populate those properties to obtain Freemarker code when the word document is converted to HTML (like ${...} or [#... /] directives).
In a later step I look for "heading 1" paragraphs to identify chapters and then split the document in several Word documents before conversion, then these documents are converted to HTML and written to temporary files.
Each document is successfully converted to HTML and fields are correctly replaced with my markers, but it behaves wrong when it writes header and footer parts: field codes are written before field values (eg. DOCPROPERTY "PROPERTY_NAME" \* MERGEFORMAT ${constants['PROPERTY_NAME']} ) instead of field values only (eg. ${constants['PROPERTY_NAME']} ).
If I write the updated document to a docx file instead, nothing seems wrong into the generated document.
If it's useful to solve the problem, this is what I do to split the document (per chapter):
clone the updated WordprocessingMLPackage (clone method)
delete every root element before the chapter's "heading 1" element
delete every root element from the "heading 1" element of the next chapter
convert the cloned and cleaned document
(actually I don't use the clone method every time, but I write the updated document to a ByteArrayOutputStream and then read it for every chapter, inspired by the source of the clone method).
I suspect it's for a docx4j bug, did anybody else try something similar?
Finally these are my platform details:
JDK 1.6
Docx4J v3.2.2
Thanks in advance for any help
EDIT
To produce freemarker markers in place of Word fields, I set document property values as follows:
traverse the document looking for simple or complex fields with new TraversalUtil(wordMLPackage.getMainDocumentPart().getContent(), visitor);, where visitor is my custom callback for looking for fields and set properties
traversing the document I look for
FldChar elements with type BEGIN and parse them using FieldsPreprocessor.canonicalise((P) ((R) fc.getParent()).getParent(), fields); (I don't use the return value of canonicalise) where fc is the found FldChar and fields is a empty ArrayList<FieldRef>; then I extract and parse field's instrText attribute
CTSimpleField elements and parse them using FldSimpleModel fldSimpleModel = new FldSimpleModel(); fldSimpleModel.build((CTSimpleField) o, null);; then I use fldSimpleModel.getFldArgument() to get the property name
I look for the freemarker code to show in place of the current field and set it as property value using wordMLPackage.getDocPropsCustomPart().setProperty(propertyName, finalValue);
finally I do the same from step 1 for headers and footers as follows:
List<Relationship> rels = wordMLPackage.getMainDocumentPart().getRelationshipsPart().getRelationships().getRelationship();
for (Relationship rel : rels) {
Part p = wordMLPackage.getMainDocumentPart().getRelationshipsPart().getPart(rel);
if (p == null) {
continue;
}
if (p instanceof ContentAccessor) {
new TraversalUtil(((ContentAccessor) p).getContent(), visitor);
}
}
Finally I update fields as follows
FieldUpdater updater = new FieldUpdater(wordMLPackage);
try {
updater.update(true);
} catch (Docx4JException ex) {
Logger.getLogger(WorkerDocx4J.class.getName()).log(Level.SEVERE, null, ex);
}
After filling all field properties, I clone the document as previously described and convert filtered cloned instances using
HTMLSettings settings = Docx4J.createHTMLSettings();
settings.setWmlPackage(wordDoc);
settings.setImageHandler(new InlineImageHandler(myDataModel));
Docx4jProperties.setProperty("docx4j.Convert.Out.HTML.OutputMethodXML", true);
ByteArrayOutputStream os = new ByteArrayOutputStream();
os.write("[#ftl]\r\n".getBytes("UTF-8"));
Docx4J.toHTML(settings, os, Docx4J.FLAG_EXPORT_PREFER_XSL);
String template = new String(os.toByteArray(), "UTF-8");
then I obtain in template variable the resulting freemarker template.
The following XML is the content of footer1.xml part of the document generated after updating the document properties as described: footer1.xml after field updates
The very strange thing (in my opinion) is that if some properties are not found, step 5 throws an Exception (ok), fields updating stops at the wrong field (ok) and all fields in header and footer are rendered right. In this case, this is the content for footer1.xml.
In the last case, fields are defined in a different way. I think the HTML converter handles well the last case and does something wrong in the first one.
Is there something I do wrong or I can do better?