You could, of course, save yourself a lot of bother and just use a Style other than Normal - as per my original suggestion.
Here's a simple macro to remove the 'automatic update' attribute from the Normal Style in both your document and its template, and to clear the 'update document styles' property in your document.
Code:
Sub StyleReset()
ActiveDocument.UpdateStylesOnOpen = False
ActiveDocument.Styles(wdStyleNormal).AutomaticallyUpdate = False
Documents.Open ActiveDocument.AttachedTemplate.FullName, , False
ActiveDocument.Styles(wdStyleNormal).AutomaticallyUpdate = False
ActiveDocument.Close True
End Sub
For PC macro installation & usage instructions, see:
Installing Macros
For Mac macro installation & usage instructions, see:
https://wordmvp.com/Mac/InstallMacro.html
As for your problem with using PrintScreen, that strongly suggests a faulty Windows installation. You should repair it.