We are seeing this quite often.
The Base Monitor service stops and posts this in the event log:
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
Even though the service is set to restart on failure, it doesn't and we have to go in and start it manually.