When I initially visited the page, I first saw the font set to Arial along with some other style differences. When I refreshed the page, I saw the updated style.
I inspected the page and saw the it had a cf-cache-status: REVALIDATED header. This tells me that the difference is caused by Cloudflare caching since the issue only appears with a domain that’s routing requests through Cloudflare, and it’s not happening with the *.vercel.app subdomain version which does not have that header.
I recommend checking your Cloudflare settings to identify the exact cause of the unexpected caching. We also have a doc covering use of Cloudflare with Vercel projects to help with setup.