New-PACertificate is written in such a way that if the cert request process has an error or is otherwise interrupted prior to completing the request, you can run the same command again and it will attempt to pick up where it left off.

Currently if request makes it all the way to completion, running the same command again will re-download and overwrite the cert files each time it's run until the renewal window.

It should probably just do nothing instead. Maybe throw a warning that the order is already complete and to use -Force if you want to re-issue.