Oct 17 2021
There was no way to reproduce it except for opening random pages until some symbols were sideways. If an issue was present on a particular equation on one page, then it would tend to still be present with that equation when refreshing (indicating a level of persistence) - but it sometimes randomly fixes itself after some time.
Oct 9 2021
I have observed this on Firefox and Chrome on desktop (the image in my original post was taken on Firefox 91.0.2 64-bit). I have also observed this on Chrome on Mobile (Android).