When running the Team Foundation Best Practices Analyzer, it failed immediately with the following message:
Cannot validate the URL provided The scan was generated using the corrected URL "%TFSServerURLValidated%".
I never seen this issue before. On the Internet I found some related blog posts here and here. But in my case the solution was a lot simpler: I ran the tool again with the ‘Run as Administrator’ option. This time everything was working as expected.