NGINX try_files always attempting to serve $uri

I'm trying to detect mobile browsers, and redirect them, using detectmobilebrowsers.com. I'm using the script as an external includes as follows:

    location /w/mobile/test/ {
        set $mobile_rewrite do_not_perform;
        include detect_mobile.conf;
        echo $mobile_rewrite;
        if ($mobile_rewrite = do_not_perform) {
          # echo "should not hit";
          rewrite ^/w/mobile/test/(.*) /w/test/$1 redirect;
          break;
        }
        try_files /templates/public-test/ /templates/public-test/mobile.html =404;
    }
    location = /w/mobile/test {
        set $mobile_rewrite do_not_perform;
        include detect_mobile.conf;
        if ($mobile_rewrite = do_not_perform) {
          rewrite ^/w/mobile/test/(.*) /w/test/$1 redirect;
          break;
        }
        try_files /templates/public-test/mobile.html =404;
    }

This is working - so when I visit /mobile from a desktop, it will correctly redirect. Unfortunately, when I now view /mobile/... from a mobile browser, it gives me a 404.

I've used the echo module and found that the try_files in the upper location block is the problem - changing it to a rewrite works perfectly fine.

The weirder thing is, I implemented the exact same code, except I check $mobile_rewrite = perform instead of the do_not_perform for the desktop -> mobile redirect, and it's working perfectly fine.

The error returned by the error.log is as follows, when visiting /w/mobile/test/\<redacted\:

\<root_directory_location_redacted>/w/mobile/test/redacted" failed (2: No such file or directory), client: 127.0.0.1, server: localhost, request: "GET /w/mobile/test/redacted HTTP/1.1", host: "localhost:8080"

Does anyone have any idea what the issue might be?