Hey @Seb
Sorry for the late reply: from our point of view, both the root and www. have been successfully registered. I see both of them. Also, the HTTP gateways do not understand that one is a subdomain of another. They just treat them as different names.
The user experience of the custom domain feature is not that great. For example, the errors that you observed are rather internal errors, which are being retried and usually disappear. So, when you saw “failed to mark acme order as ready”, it didn’t mean that this registration failed. It just meant that we had an issue with one step and will retry it soon. That’s also what happened and your registration succeeded in the meantime. Ideally, we would not expose such errors as they are not actionable for the user and rather confusing.
We have conducted a survey here and will get to improving it towards the summer.