I was using Roboto, but after swapping my fonts to Helvetica Neue it seemed to have fixed the issue. I suspect it only impacts specific fonts, and maybe custom web fonts.
I'm not sure why my header font is changing between modes. I tried clearing my cache and cookies and testing on different browsers. I feel like this might be a bug?
http://chriszyu.com/
Screen Recording 2023-08-07 at 3.24.31 PM.mov