Looks like it's back to normal now. I wonder what happened.
Totally our doing and not a hack of any kind. Team is writing this up and we'll blog about what went wrong.
Sorry about this error.
If it wasn't DNS, then I guess it must have been the reverse-proxy? In that case, if clickfunnels had uploaded their own public CA (or hosted it on pages.dev, which doesn't add sni.cloudflaressl.com to common-name/dns-name), would the redirection still have been without browser errors?