A solution that helped me repair the document permanently was provided by a user on a social.technet thread.
Having been through the same frustration, here is how I've successfully addressed this problem.
By Example
Given: Heading 1 ordered list style has the number portion blacked out.
Place the cursor at the text formatted with the "black-boxed" Heading 1 style.
Use this "Classic Menu" Alt-key shortcut: Alt-O, N -> the "Classic Menu" equivalent of Format, Bullets and Numbering -> you will now see a GUI dialog with four tabs: Bulleted, Numbered, Outline Numbered, List Styles -> select the List Styles tab.
The List styles frame offers a selection 1/1.1/1.1.1, make this selection and click OK.
At this point, the Heading 1 text should no longer be "black-boxed" - you might need to adjust your margins and/or tabs, which you can do from the ruler, and then do a "Update Heading 1 to Match Selection".
Et voilà!
Once doing that, I was able to use the 'Define new Multilevel List...' wizard to modify the styles to my liking (note: I did not link any headers to the list levels, as that seemed to raise the ire of this nasty bug). I found that wizard in the 'Multilevel List' dropdown (within the Paragraph ribbon tab), having selected the List style added in the block-quoted text first.