We notice that when using Chrome, sometimes text does not appear. No errors show up in the console.
The issue only occurs when we are self hosting the web fonts for, and we see that while the main css file is downloaded, none of the subsequent font css files are downloaded (which are in FireFox for example).
The web fonts are only used if the font is not embedded in the PDF. This is why the issue might not occur with some PDF files, or other PDF files might partially work.
For the chrome issue, while we don't fully understand why, PNaCl fails to download the .css files if they are gzip/brotli compressed.
Please make sure your server does not compress the .css files that we distribute for font loading.