Task Engine Not Starting 追蹤

I have a piece of code that fails intermittently. once it fails it continues to fail

var taskManager = new TaskManager();

if(taskManager.TaskEngines.AliveCount == 0)
{
   log("taskManager to be started")
   taskManager.Start(1);
}
if((taskManager != null) && (taskManager.TaskEngines.AliveCount != 0))
{
   //....Print 
}

When code first fails, the first if statement is entered without exception then it doesn't enter the second if statement. It looks like that the line taskManager.Start(1) is not working