Automated triage: As designed
Thank you for reporting this issue. When our upgrade-check server returns an error page, the check catches it and records one server error log entry showing what came back. The next automatic check runs as normal, and you can run the check by hand from the upgrade-check page in the control panel. The entry records an outage on our side and doesn't mean anything is wrong with your forum.
This is an automated assessment. A member of staff may review and update it.