One specific Chinese character ? not displaying on some browsers

Hello,

I have a bug with this specific Chinese character : ?

It does not display in some browsers, like all Android browsers, some browsers on PC but not all, difficult to have details about that. There is no problem with any Mac desktop or iOS browsers. And it’s just that character… the others are fine.
I have been trying to change the Chinese font with smth very common like :

font-family: 'Open Sans', "宋体", "SimSun", "华文细黑", "STXihei", sans-serif

but it does not change.

I thought it was a theme problem until I tested on another WP site, hosted on another server… and I had the same problem..

you can try over there :

check the language switcher. The second character of 中? should not been displayed correctly for some of you. especially if you check with and Android phone 5.1.1
and there :

I have been trying this character in other parts of the website, page title, menu, simple text… it does not work, and it seems that it’s the other one.

Anybody knows about this bug ?

And most of all how to solve it ?

thank you in advance for any useful answers.