Security Heads from Ninja Firewall not working + Uninstall leftovers

I’ve been using this plugin for a while and although it’s served me well, I reply on a new security configuration that seems to be incompatible with this plugin.

WP Fastest Cache developers should absolutely find a way to properly support security headers from other plugins as security takes precedence before speed, Always.

At any rate, there are also nasty leftovers upon install, which should not be the case:

/wp-content/cache/tmpWpfc
/wp-content/cache/wpfc-minified