IOS 15: WebAuthn catches error but still prompts user

Hi. The registration process with WebAuthn works fine and expected. As we use the same code on both android and ios, we dont use discoverable credentials, but instead saves the credential-id in a cookie. If an user deletes his cookie, we can not see if the user has registered previously without prompting the user for registration again. This is okay, and if we get an InvalidStateError (because the user is already registered) we let the user think he has registered again, and just creates a new cookie.

The problem is: When the navigator.credentials.create is called, the InvalidStateError is catched immideately, before the user have time to do anything about the faceID prompt which shows. When the InvalidStateError is caught, the Registration Completed page shows. This means the completed page is shown behind the face-id prompt, which is very confusing for the user. How can the registration be completed if the face-id prompt is not finished?

On Windows, the error is not thrown before the user has completed the faceid prompt, which means the registration-process is experienced exactly as a first-time registration.

Is it a bug that the prompt is shown after the error is thrown? Any tips to how i can work around this? If this is not the right forum to ask - where is a better place?

Best regards, Nina