You've requested a page on a website (b.localhost) that is on the Cloudflare network. Unfortunately, it is resolving to local or disallowed IP address.
Please see https://developers.cloudflare.com/support/troubleshooting/http-status-codes/cloudflare-1xxx-errors/error-1002/ for more details.
If you are the owner of this website:
you should login to Cloudflare and change the DNS AAAA records for b.localhost to resolve to a different IPv6 address.