Corrupt UI In Incognito and Private Browsing

I have a relatively new self-hosted Discourse site behind a Cloudfare proxy.

Today, a user complained that when they went to log in, the font was enormous and the username/password fields were missing. To verify it wasn’t a general problem, I fired up an Incognito window (since I was already logged in from a different browser tab) and saw the same issue. Here’s a screenshot of the area below the site logo (the logo is rendering twice by the way):

Same thing in a private window in MS Edge. No problems at all for me with either browser when using a normal browsing window.

The user was not using a private window explicitly but they were using a company computer.

Is this a known issue and if so, how can I correct it?

Easiet: Turn off cloudflare proxy. Next easiest: Turn off cloudflare speedups.

See Using Discourse with Cloudflare: Best Practices