Bullet list applying in error to headings above

Build ID: 1:6.0.1~rc1-0ubuntu0.16.04.1~lo1

-on my laptop:
CPU threads: 2; OS: Linux 4.4; UI render: default; VCL: gtk2;
Locale: en-US (en_US.UTF-8); Calc: group

The file is .docx, but I think this has ocurred with LO files too.

Symptoms so far:

With headings defined to level 4, making a bullet list below heading 4 adds bullets to all the level 4 headings in the document.

What is the paragraph style of the bulleted list? if it isn’t a matter of style, I saw a similar phenomenon in this question. It seems to be related to compatibility with .docx. Fewer problems with doc. No real cure for it, except paste document content as plain text in a new .odt and reapply formatting. Sigh!