There is an issue if you need to take slaves offline when idle as this takes the workspace offline - which triggers another build. The slave comes online to build. The slave times out and goes offline. The workspace is gone and another build is scheduled that brings the slave online again. The job then builds perpetually.

If more than one slave can and has serviced a job and if the last used slave goes offline, another build kicks off even though there are other slaves albeit with older workspaces that can be used for SCM polling to establish the real need for a build. This may be a specific ClearCase SCM related issue.

I spotted the SCM poll reporting build required as workspace is offline. Which is not reported in the changelog.