How to customize fonts for PowerBI card visual labels

For a company dashboard in PowerBI I need to use the specific global font Univers LT Std 45 Light which is part of the Windows 10 standard fonts, however, it is not accessible in PowerBI Desktop by default. From sources online including the original documentation, I have learned that customization can be achieved by importing theme.json files that contain styling parameters.

After a "successful" import, most of the visuals change their fonts automatically. For text boxes I had to change the font manually but at least it now shows up in the drop-down menu. BUT: Card visuals only adapt their title, however, not the label itself. I really need all labels on my dashboard to have the same font, otherwise it looks weird. What am I doing wrong?

Here is my theme.json file:

{
   "name":"myTheme",
   "textClasses":{
      "label":{
         "fontFace":"Univers LT Std 45 Light"
      },
      "callout":{
         "fontFace":"Univers LT Std 45 Light"
      },
      "title":{
         "fontFace":"Univers LT Std 45 Light"
      },
      "header":{
         "fontFace":"Univers LT Std 45 Light"
      }
   },
   "visualStyles":{
        "*":{
            "*":{
                "*":[{
                    "fontFamily": "Univers LT Std 45 Light"
                }]
            }
        }
    }
}

Solution

After reinstalling the software and many tests I've found the answer: The theme import is working properly but ONLY for visuals that

haven't been styled manually regarding the concerned attributes (fonts in my case)
are added after the import of the theme.json

but not for ALL visuals as expected.

So easy solution: Just start over with your dashboard and import themes before adding anything. But seriously, I think this is a bug. Styles shouldn't be "frozen" just because they were changed at some point.