Strange OneNote font issues

Hello all,

first, I'm not a native english speaker, pls excuse some mistakes. 

I have a really strange problem. After some time, OneNote (and also OneNote for Windows 10) is missing the standard front "calibiri" (like you will see on the photos attached, OneNote is using the "missing-characters"). There is no problem with this font, that's for sure. I can use calibiri in every other Office/not-Office application without any problems, and I also tried to reinstall calibiri ... nothing helped.

The only way, that I have found to fix this, is to reinstall OneNote and OneNote for Windows 10. After that, everything is working fine ... sometimes for 10 days, sometimes only for 2 hours. That's really annoying. 

I had this problem with Office 2016 and also now with Office 2019.

I have really no idea, what is possibly causing this ...

Any ideas?

Thank you very much 🙂