Whipped up a quick plugin to place in mu-plugins, functions.php or a regular plugin:
function fix_nginx_cache_path($cache_path) {
$cache_path = defined( 'NGINX_CACHE_PATH' ) ? NGINX_CACHE_PATH : $cache_path;
return sanitize_text_field( $cache_path );
}
add_filter( 'default_option_nginx_cache_path', 'fix_nginx_cache_path' );
add_filter( 'option_nginx_cache_path', 'fix_nginx_cache_path' );
add_filter( 'pre_update_option_nginx_cache_path', 'fix_nginx_cache_path' );
function fix_nginx_auto_purge($auto_purge) {
$auto_purge = defined( 'NGINX_AUTO_PURGE' ) ? NGINX_AUTO_PURGE : $auto_purge;
return absint( $auto_purge );
}
add_filter( 'default_option_nginx_auto_purge', 'fix_nginx_auto_purge' );
add_filter( 'option_nginx_auto_purge', 'fix_nginx_auto_purge' );
add_filter( 'pre_update_option_nginx_cache_path', 'fix_nginx_auto_purge' );
Then set NGINX_CACHE_PATH (full path string) and NGINX_AUTO_PURGE (1 or 0) in wp-config.php to your needs.
Hope that helps ??