HTML minify encoding problem

I am using W3TC 0.9.4.1 with WordPress 4.4. My website is a Japanese website, when I enable the HTML minification then few characters are replaced by ?, otherwise the page looks fine.
It seems there is an encoding problem. I have correctly emptied the cache, when I disable this option then the page is rendered well. The metatag <meta charset="utf-8"> is specified. I’ve tried to play with the settings but the result is still the same.

Maybe there is something to add on the server side or the .htaccess?

https://www.ads-software.com/plugins/w3-total-cache/