ELZ, I agree with Bjarney, you have a shutdown waiting to happen. If I was to bet on it 2:00AM when you dead tired. Noise out of the trip unit is bad.
I do thermal imaging as part of my job. Find someone in your area to do an infarred scan of the breaker. This is a lot safer than opening the breaker front cover live. I am not saying you can't do this, just infarred is safer and less likey to cause the breaker to trip. Also do the millivolt drop test across the breaker.
