"Content is not allowed in prolog" if response returned contains headers and stuff about phase4 HOT 7 CLOSED

@Nullable
  public static Ebms3SignalMessage parseSignalMessage (@Nonnull @WillNotClose final AS4ResourceHelper aResHelper,
                                                       @Nonnull final byte [] aBytes) throws Phase4PeppolException
  {
    // Read response as XML
    Document aSoapDoc = DOMReader.readXMLDOM (aBytes);
    if (aSoapDoc == null || aSoapDoc.getDocumentElement () == null) {
      Session newSession = Session.getDefaultInstance(new Properties());
      InputStream inputStreamObj = new ByteArrayInputStream(aBytes);
      try {
        MimeMessage mimeMessageObj = new MimeMessage(newSession, inputStreamObj);
        String contentType = mimeMessageObj.getContentType();
        part = (String) mimeMessageObj.getContent();
        part = part.replaceAll("\\<\\?xml(.+?)\\?\\>", "").trim();
        part = part.substring(0, part.lastIndexOf('>')+1);
        aSoapDoc = DOMReader.readXMLDOM (part);
        if (aSoapDoc == null || aSoapDoc.getDocumentElement () == null) {
            throw new Phase4PeppolException("Failed to parse as XML");
        }
      } catch (MessagingException e) {
        throw new Phase4PeppolException("Failed to parse as XML", e);
      } catch (IOException e) {
        throw new Phase4PeppolException("Failed to parse as XML", e);
      }
    } else {
      part = new String(aBytes);
    }
....