Custom Font reverts to default

[Kohwitheflow]

Hi.
So I use a custom font for many of the headers on my site, which I uploaded in the 5 recommended formats.
This custom font displays fine on desktop view, but when visiting the page on mobile every instance is changed to a large default font. I really don't know what to try.

I have two versions of this site in different languages and on one it displays fine but on the other I have this problem with all the custom fonts in mobile view.
Any suggestions??

Thankyou.

ps. I attached images, in the first two you can see how the font is displayed in edit mode and desktop view, and the third is a screenshot of viewing on mobile.