I have an email that renders almost perfectly on Yahoo! mail app. For about 20 seconds, longer if you scroll through the email. After that, the font-size seems to kick up

I fixed an issue that resulted from this by targeting Yahoo iOS. However, the main issue is still occuring. I've never seen this with any other email -- but 1. I don't often test for Yahoo! mail app as we don't have many users opening on it. 2. I didn't code this email initially, I'm just fixing other people's mistakes.

Has anyone else experienced anything else like this?

Screenshots:

https://photos.app.goo.gl/6xCaZSjRejoO8Mv43