Please see this screenshot:

http://screencast.com/t/GFJMAzAis9v

As you can see, I will bold some text in any section which starts off as #1 (like section #2, #3 etc.)

I will edit the rest of the document and the boldness has disappeared but only for section #1. This happens for multiple sections in the document using the same styling.

What could be causing this please? Any pointers would be much appreciated.



Thank you!

You should use styles for different formatting.
For instance, consider using the Strong style for text you want to be Bold.

Understanding Styles in Microsoft Word
You should turn off automatically update styles as an option.

Your problem tells me that you are doing something different in the text that changes than you are doing in the text that is not changing. This may be related to the automatic settings or to an Autoformat as you type setting.