Hi,
me again. And I found the issue! It was because of the redirects made by the plugin in the .htaccess file.
Unfortunately those redirects will cause the server to load directly the cached files instead of letting php do the dynamic content update?!
I found it out by using the "Test Cache" button of the plugin where a message appears which says that I am using PHP cache and mod_rewrite is still declared in the .htaccess file. Once I deleted the entries created from wp cache the dynamic content replacement works with all the settings as it should.
It would be good if the plugin would remove those entries when changing the cache mode. I understand that sometimes it is not wanted to remove those explicitly. But when changing modes the user could be asked if he wants to keep those changes.
It would have save me a lot of headaches.
Otherwise this plugin is a great tool to make your site really faster with a lot of settings to fine tune it to your needs!