Let's Encrypt response on renewal: Order's status ("valid") is not acceptable for finalization

Sometimes the renewal of a certificate for an existing domain fails with the error below. Fixing this can be done by removing the existing certificate from the filesystem, and then going to the URL again. How can we prevent this from happening?

```
Request failure: STATUSCODE=403 REQTYPE=post
{
"type": "urn:ietf:params:acme:error:orderNotReady",
"detail": "Order's status (\"valid\") is not acceptable for finalization",
"status": 403
}
```

Start by tracing the Let's Encrypt renewal and finalization flow, focusing on how an existing certificate on the filesystem affects the request. Reproduce the 403 orderNotReady response, compare behavior after removing the certificate and revisiting the URL, and confirm that renewal no longer requires manual filesystem removal.

Written by the indexing model from the issue text.