Browser Cache Keeps disabling

I can get my browser caching enabled ok. But it seems to keep disabling. Further, if you go onto this site (using chrome): http://www.swoopingeagle.com , it seems to keep refreshing every 5 seconds.

Error:

Browser Caching is not working properly:

- Your server may not have the "expires" module enabled (mod_expires for Apache, ngx_http_headers_module for NGINX)
- Another plugin may be interfering with the configuration