Hi Sonali,
Thanks for your inquiry. First of all, we always encourage our customers to use the latest release versions of Aspose.Words as it contains newly introduced features, enhancements and fixes for issues reported earlier. You can give the latest version (11.6.0) a try by downloading it from the following link:
https://releases.aspose.com/words/java
Secondly, please note that there can be a maximum of only one HeaderFooter of each HeaderFooterType per section. Talking about headers, there are of three types i.e. HeaderFirst, HeaderPrimary and HeaderEven; so up to three different headers are possible in a section (i.e. for first, even and odd pages).
In your document, there found to be three Sections. The orientation of pages in first and third Sections is portrait; however, the orientation of pages in second Section is landscape. I would suggest you please read the following article on specifying how headers and footers are exported to HTML, MHTML or EPUB formats:
https://reference.aspose.com/words/java/com.aspose.words/ExportHeadersFootersMode
Moreover, while using the latest version of Aspose.Words i.e. 11.6.0, I managed to reproduce this issue on my side. I have logged this issue in our bug tracking system. The issue ID is WORDSNET-6794. Your request has also been linked to this issue and you will be notified as soon as it is resolved.
Sorry for the inconvenience.
Best Regards,