Another formatting issue in a project deliverable: Heading numbers blacked out

I have been working with project deliverables since I started working with projects (which is back to 2009, if I recall well) and since then I have authored and contributed to dozens of them; not only I was usually the one to transform ideas and bullets into text (I love writing texts anyway!), but I was also one of those paying attention to the details, and when it comes to document formatting, this is something that can make the difference. The latter made me one of the frequent deliverable reviewers, too :-)

Why am I writing this? I recently received yet another project deliverable (a dissemination one) for comments and contributions - on top of that, I noticed an annoying issue in the numbering of Level 3 and Level 4 headings, which caused the corresponding heading numbers to black out.

Image source: http://tomtalks.uk/2015/06/fixing-microsoft-word-blacked-out-numbers/

My first move was to inspect the formatting of the specific headings (right click on the Heading 3 -> Modify); however, I could not find anything strange there. Then, I just Googled it: It seems that it is a pretty common issue, caused by a corrupt template. The proposed solution was the following:

1. Put your cursor on the heading just right of the black box
2. Use the left arrow key on your keyboard to move left until the black box turns grey
3. Use the keyboard combination ctrl+shift+s, the dialog "Apply Styles" should appear
4. In this box, click "reapply"

I did that, but I had to do it for any Level 3 and Level 4 heading, which was time consuming; then I saw a user proposing another step:

5. Go to a fixed issue, then right-click on the corresponding Heading button on the top menu of MS Word and click on "Update Heading 3 to match selection". 

That was quick! I felt pretty good about the solution, saved my document and exited. However, when I opened it again just to make sure, the issue was still there, with the bad formatting still around! No matter how many times I tried, the issue would re-appear each time I opened the document. 

And then, I thought I should try something (not suggested by any user):

I fixed the issues, saved the document as .doc (not .docx, as the original) and check. Indeed, the issue was gone (along with some details of the tracking changes but not the tracking changes itself; however, this was pretty minor, as the revisions were still marked and plus I was informed about that before I saved the document in .doc). The only thing I had to do was to save the document as .docx again and check it for the last time - and it was ok!

I was just pissed off, because it was a pretty busy day and I had to spend time on this workaround... :-X