generic mirror giving 400 errors

I have setup a CNAME to my website and symlinked the wp-content directory under the subdomain folder created by Bluehost. This my poor man’s way to setup a self-hosted cdn without having to duplicate the content.

If I enable the option “Host minified CSS and JS files” when doing a generic mirror under the CDN optoins I get 400 errors for the minified files. No other files are having issues, just the minified files.

I have determined that only 2 of the files are created under /wp-content/cache/minify/000000/ when accessing the file from the CDN. The two files are *.css.old and *.css.gzip.old. The *.css and *.css.gzip files do not get created (or replace css with js.) If I then access the resource from the primary domain these files get created and I can then access them on the CDN. What have I done wrong so that these minified files get created properly?

I would have expected the primary site to create the file, mirror them through the symlink and they are then available through the cdn.

https://wordpress.org/plugins/w3-total-cache/