[Plugin: WP Super Cache] Big Problem

I got a big problem after installing this plugin. From time to time when I refresh my browser or want to access a page, it tries to download the pagetitle.php as file. For example… I want to open the page contact.php my browser starts to download a useless empty contact.php file.

With Safari it’s even worse becaue it happens many more times. What could cause this problem? Thank you

https://www.ads-software.com/extend/plugins/wp-super-cache/