If you want Kovid to take a look at your DOCX conversion issues, you'll need to provide the information outlined in this sticky thread ==>>
How to ask a question about conversion problems
Try the Mammoth converter ==>>
Mammoth · DOCX->HTML, and import its output into calibre, or use Sigil's DOCXImport plugin (it's a wrapper around Mammoth) see ==>>
Sigil ePub Editor
Try
Toxaris's eBook Tools MS Word add-in
There's also a plugin for Writer than creates ePUBs, I don't have a link for it, but should be easy to find.
BR