steps to reproduce:

1. ASSERT: make sure that you have a build that failed (ex. launch a nodejs build and shut down your vpn. The build will fail because it cannot connect to the registry)
2. EXEC: in Properties view: select "Builds" tab and choose your erroring build. Choose "Build Log..." in it's context menu

Result:
You're told that you cannot get the logs for an erroring build. You therefore cannot have insights on why your build failed:

The webconsole allows you to inspect those logs: