I believe the 422 error when you attempt to renew the domain is related to or outright caused by the problem that is causing the 500 error when you attempt to update the Billing Address of the Account.
It appears that Cloudflare is performing some kind of validation before processing the payment method. The only item I have had any problems with is the Billing Address of the Account. I’ve even tried to renew the domain in the business account using the same payment method and payment address that work just fine for my personal account. The only difference is the billing address of the account…which I cannot change on the business account.
I’ve got an open ticket with billing but keep being asked to update the payment method and payment address then try again.
Hopefully you’re getting better support!