Hi Cloudflare support team,
We have this issue with Cloudflare CDN. Out domain is kyber.network and using a custom SSL certificate issued by Cloudflare.
We mapped the subdomain developer.kyber.network to 22.214.171.124 using an A record.
Yesterday, I deleted that A record and remap that subdomain using a CNAME recore which point to d1khr3ex61w5s1.cloudfront.net.
After that we encounter 526 SSL error in some regions (i.e. the US), and it works fine in some other regions (i.e. Vietnam).
We also have this scheme works fine on a development domain which use only Universal Cloudflare Cert.
We hope that Cloudflare support team can give us more insight about this issue.