Something that was brought to my attention by a colleague of mine the other day. When running the Most Common Alerts report in SCOM 2012, if you select more then 15 for your top N alerts then the report renders with multiple blue, red and green blocks. I then tested on my SCOM 2012 environment and discovered the same situation.
We logged a support call to MS on this one and they were able to replicate the issue in their lab environments. They have since provided us with a fixed version of the report which has been amended to render better for higher amounts of alerts.
In order to update the report follow these steps:
1. Browse to the report server manager http://server/reports
2. Open Microsoft.SystemCenter.DataWarehouse.Report.Library
3. On the drop down menu next to the report Microsoft.SystemCenter.DataWarehouse.Report.MostCommonAlerts select download and make a backup of this report
4. Then click on upload File
5. Browse to the updated .rdl file
6. Select “Overwrite items if it exists” and then click OK
7. Refresh the Reporting Pane in the SCOM console and run the report