I managed to fix it slowly by doing the following...so it affected only heading 3 level. But went to the first H3 heading in the document then changed the numbering to none. Then re-selected the numbering 1 H1, 1.1 H2, 1.1.1 H3, etc. from the list. This corrected the numbering and sub-sequent H3 headings in the document but not all. It corrected like maybe 20 of them, then it stopped at a particular problem H3 heading. And would repeat the above process again...and work through the document.

I was hoping I could select all H3 headings in the document and just correct them all at once. Should I not be able to select all instances of H3 style, remove the numbering then re-apply as I did above? And this would remove and readd the section numbering for ALL instances of H3 headings in the document.

Let me know if none of this makes sense...