They are addressing the problem and will publish guidance on GOV.UK.
Capital Gains Tax refunds can't be given within Self-Assessment.
To claim the refund, contact HMRC after submission through the normal channels, such as the agent line or customer helpline. HMRC will review the claim and make any refund due. The method of repayment is likely to be determined by how the customer completed the repayment section on the return.
There's no need to change the online CGT payment for Property Disposal return. The repayment will be dealt with fully through the self-assessment return process.