How to permanently localise and delete a header?


I have tried numerous times to localise the header region, that for some reason has been globalised and now at times shows a newsletter sign up form that really should not be there? The header region appears every time you create a new page in upfront, but in these cases without the newsletter form. In blog page template, in the 404 page and in the preview of coursepress pro course units not yet publisehd, there is also the newsletter form in the header region.

I have tried to localise the header everytime it appears in the new page template, but this does not seem to affect the template itself. How to get rid of this header region for good?