SSL Caching prevends https requests

I use the W3 Total Cache Plugin for Wordpress.

If I enabled "Cache SSL (https) requests" in W3 Total Cache and testing my site at for security reports, then I get only one time a positive response.

Anyone know I can fix that?

The problem is when I disabled the SSL Caching the 304 header (Last-Modified) don´t works anymore.

If I clear the cache then it works again and the response is positive. But i can´t clear the cache every time after an request for every user.

Or I have a wrong thought ?