A problem document is not a bug.
You have 2 separate list styles, one for the blue headings and another for the list below the headings. Instead, create a single outline numbered list styles that combines both. Then you don't need to restart the numbering after a heading, the numbering will restart by itself.
Here's is Shauna Kelly's tried and true method for setting up outline numbering: How to create numbered headings or outline numbering in Word Though her article refers to setting numbering on heading styles, you can actually use any Word style as part of an outline numbered list style.
Set the numbered body text (the text you are trying to set back to 1) as the second level. For that level, check the option Restart list after and select Level 1 in the dropdown. It will be much easier to use, once you get it set up.