Word keeps on losing the numbering of headings

[Gerry Wolff]

I have a problem with Word 2010. When I save and close a copy of the
document I am working on, the numbering on level-3 headings is lost.

I have done everything I can to try to make sure that the format of
level-3 headings is saved in the 'dotx' file.

I have also run a repair for the whole of Office 2010.

But the problem persists.

Does anyone have a solution?

With thanks.