The alerting service was bunk in 4.1.3 and 4.1.4. It is suppose to be fixed in 4.1.5.
When a thread fails a health check its going to fail for the users that are utilizing those particular threads. So in your case "Thread 175C, utilization=0.0000%, failed health check 121 times" if there were 10 people on that thread 10 people will not have service. When you start seeing threads failing it usually waterfalls over time...meaning more and more threads are going to fail.
How many users do you have? What is your current threading model on the BES and what is it optimized to? Also what lvl is your logging set to right now?