You didn't mention if this was a residential panel or something else, but if the "something else" is a commercial or industrial application, high current flow is a possibility (as noted), and it's also possible there's a small step-down transformer mounted nearby to handle a low-voltage control circuit. Could have a mounting screw coming loose. Otherwise, it's definitely worth an electrician's time to tighten everything down. Snap-in breakers don't just come loose, if they are loosening up (or if the busbar is coming loose) there's a reason and it needs to be addressed.
Within the past couple years I've helped two different friends inspect and repair some electrical deficiencies in 70s-vintage homes and one of the first things that got done was to replace a number of breakers. Depending on exposure, exterior-mounted boxes can take a lot of thermal cycling and moisture ingress over the years and things corrode or get sticky. Any breaker that makes scraping noises, throws incorrectly, or doesn't 'catch' easily needs to be replaced. In one case, we even found a breaker that could not be tripped off -- the handle would catch about halfway without breaking the circuit, then spring back to the 'on' position. Eek
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