Does WP do some kind of redirection prevention?

I have a chunk of code that executes correctly, and then tries to redirect to:

http://xampp.dev/wordpress/wp-admin/admin.php?page=zp_wp_plugin_slrs_top

I know the URL works, because if I just paste it into a browser window, everything works.

So I've tried:

$location = admin_url($adminurl);
wp_safe_redirect($location);

That didn't work. It redirected me to the main admin page. I wasn't sure I could get the URL to be one of the "approved" URLs (if you know how to add this, I'd appreciate the hint). So I tried:

$location = admin_url($adminurl);
wp_redirect($location);

That didn't work. It redirected me to the main admin page. So I tried:

$location = admin_url($adminurl);
header("Location: $location", true, 302);

That didn't work. It redirected me to the main admin page. So I tried:

$location = 'http://www.google.com';
header("Location: $location");

In every single one of these instances, WordPress redirected me to the main WordPress dashboard page. So I'm starting to think WordPress has something getting in the way.

Can anyone explain what it is WordPress is doing and how to get WordPress to allow me to do these redirects (which are necessary for my app)? Thanks.