A new one I'm getting lately is when I lose a relay or module the building owner wants to know why no preventive maintenance was performed to prevent this shut down.

I pointed a light bulb and said can you tell me when that bulb will quit working, his answer was no. Any electrical component can go out any time. We do perform controller maintenance and tighten all connections, ohm out all contacts on relays and check the resistance on the coils of the contactors but that only tells me so much. He was not amused by my explanation.