This is response to traffic on email from Sierra Remote where the Boltwood file was getting locked and preventing people from observing. Since they are in charge of protecting equipment, I slowed the polling way down. This helped them mitigate the locking issues.
Also,
Mark deRegt points out in this thread that they often open the roofs to cloudy skies.While hot unsafe, it causes the Scheduler to start observing and the plans quickly fail, piling up those weather failed plans.
Add "cloudy" and "very cloudy" in addition to Roof Closed to the conditions for which "unsafe" is reported.