Latin-ext font shows fine in Chrome nad Firefox & not fine in Edge and Vivaldi

Hi,
I have a page on http://isitup.site. Site include some texts in Slovene language with local accented characters. I loaded font which support latin-ext (Montserrat and Open Sans).
Web page show fine in Chrome or Firefox but not fine in MS Edge or Vivaldi browser.
What could be a problem?
Thanks.