There are two things we would like to point out about Shield:

  1. Shield does not use or modify the .htaccess in any way. We don’t write to any core .htaccess files.
    Instead, Shield examines the data in the requests and then allows or blocks WordPress from loading depending on the rules you have chosen.
  2. Shield does not setup any sort of redirects

If you can't get a 301 .htaccess redirect to work, you can demonstrate that Shield isn't causing the redirects if you temporarily disable it. 

Important Note: As 301 redirects are normally cached by the browser, and also by caching plugins on the site, we suggest you to ensure you're factoring all of these when debugging. While you may have disabled or removed any item causing 301 redirects on your site, your browser may still be performing the redirect.