Embedded fonts don't work on Windows PowerPoint after the new update

Question

I work for a company that generates .pptx files programatically. As part of this, we embed font files in the generated document so that the fonts render on every user's system correctly. This embedding has been working correctly for many years, but it stopped working on new versions of Windows PowerPoint. The rendering was still working on version 2407, but when updated to 2410 (build 18129.20116) they no longer work (it could have been a version in between these that broke it, but my update went straight from 2407 to 2410). The font rendering still works on the latest version of PowerPoint on Mac. The next day I updated again to 2410 (build 18129.20158) and the same files that had been rendering incorrectly the day before were now rendering the fonts correctly. However my colleagues (and our users) are still experiencing issues on build 18129.20158.

In terms of what is wrong: the file still opens correctly and is fully editable, but the text renders using the default system font, presumably because it can't read the embedded font file.

The fact that we haven't changed our code at all and that the behaviour was different for the exact same file on different days leads me to believe that this is due to a code change on Microsoft's end. Wondering if anyone else has experienced this issue and/or knows what changed for font embedding in the latest updates.