Sometimes (a lot of times) the breakers just go bad. Well, around here anyway; probably a power quality issue. I have multiple, multi-story military barracks buildings (dormitories). The first thing I do is replace the breaker with one I know works correctly; most of the time that is all that's needed. When there is a real fault somewhere, I simply isolate each device and piece of equipment in the circuit 'til i find what's causing the fault and make repairs/replacements as necessary.
I'm trying to get my company (DON) to get me one of those new-fangled circuit analyzers that could maybe tell me up front what's happening in the circuit first. But, being that the government continues to be short of funds the likelihood of that happening is slim.