The Buffer Cache Hit Ratio alarm has been deprecated in Spotlight. In many environments it really doesn't provide any meaningful information. There are now 2 alarms that are available that cover the case, IO Wait Time and Performance Health.
It would seem there might an issue in the upgrading of Alarm Actions that contained a clause relating to the Buffer Cache Hit Ratio alarm which can result in some problems. Recreating these alarms from scratch shold solve the issue.