The server is running normally and serving requests without any problems, but suddenly I started getting errors from time to time
The service you requested is not available at this time.<p>Service error -27. <ins>That???s all we know.</ins>
The error is an HTML page with Google logo and other Google branding. The error is not reported in the logs, and nothing indicates in Google Console that there is an error. After that calling the same service, or any other would work just fine.
I'm using Restlet as a web server.