When the provider responds with cancellationId=null it should be the trigger to call a manual cancelation, however, it is not happening. The protocol expects at least 3 requests to have failed before starting the manual cancelation and changing the status of the payment and transaction to "canceled".

The issue occurs when the payment method uses a payment app and due to this behavior, explained earlier, the app at the checkout never receives a notification of the cancellation and loops indefinitely.

It is not possible to simulate.

It's possible to implement a manual process of proactively canceling the transactions via API or by clicking the cancel button on the order page.