I'm on Win10/Edge/MSO 2010.
I copied 'htm' content into Word: paste option "keeping source formatting."
I saved the file as .docx and closed word.
In LOGOS 6 -- TOOLS, PERSONAL BOOKS; entered title etc., ADD FILE, BUILD.
Received the attached log file showing 44 errors and 6 warnings. The ERROR text does not make sense as the option concerning compatibility was not available, i.e. this is only available when saving an earlier Word .doc as .docx.