Instagram In-app browser loading site incorrectly

When I open my site through Instagram’s in-app browser, a few parts of the CSS get ignored, like the mix-blend-mode and the type size. On refresh it loads fine, but initially it’s all messed up. I have initial-scale="1" set, and tried setting media="screen" as well, but neither of those things solve the problem. The site is fine in Slack and Gmail’s in-app browsers, so I think it may just be Instagram.

Also, on some iPhones, when you look at the site in Safari and zoom in, it disables the mix-blend-mode. This isn’t a huge issue, but maybe it could provide some clue about what’s going on.

The site is if you want to look yourself.