Thanks for your reply.
Unfortunately I don’t have the knowledge to know which file has the CSS. I added various CSS files to the “exclude” section but none of them made a difference, example:
/wp-content/themes/nikkon/style.css
Fairly sure wherever the font “Dosis” is being used it is appearing in a different font when the Process CSS files is enabled.This font is the one set in Appearence —> Themes —> Customize —> Nikkon Font Settings.
The title/tagline/menus/headings all appear in a different font, however the body text appears correct (Open Sans I think).