It's hard to find a routine check-list that doesn't have this sort of problem. We've investigated the idea of inserting deliberate errors in the diagnostics systems used by our engineers for exactly this reason. Sometimes even though a reading is OK we could show red. The system logs would show that this has been done, and if the engineer report doesn't, we know the check-list hasn't been followed properly.<p>But it's hard. We have intelligent, clever people, and mundane checks don't come easy. In some cases the more clever and capable someone might be, the worse the problem becomes.