In UIM 9.0.2 the Report Scheduler may fail to start scheduled tasks. This is a known issue.
If you experience this problem please reach out to CA Support for a copy of ump_reportscheduler_9.0.2_HF1_test.zip.
After deploying this patch on a multiple UMP environment you might experience the tasks getting triggered twice. Deleting and recreating the tasks should resolve the problem.