The font we set in Theme style > typography > body is also applied to some parts of the builder, such as element names and the Context menu. Of course, this has happened with the Context menu on some of my websites and I don’t know what the difference is right now.
Works fine on my sites.
However its the first time I’ve seen the new Style popup thing and have to say its is extremely unwieldy and confusing. Will try and put my thoughts together and make a new post.
Unfortunately, I can’t reproduce the problem either. Just check the right-click menu with the dev tools and see which styles are applied there and where they come from.