We had a breaker covering the bathroom lights that would trip every now and then. One leg had the three ceiling lights, one leg had 6 vanity lights. First time, we noticed a problem was a time that all lights were on, and it tripped.
Well, obviously, it must be too much load for the breaker. Then a month later, the lights started flickering every now and then. We thought it was a bad breaker, dealer looked at it, and found a bad grounding bar, and fixed that.
A few month's passed, and then occasionally if either set of lights were on, the breaker might trip, or the lights flicker some. We ignored it. Then on a maintenance trip to the dealer, they were working on the electrical, and had the breaker trip on them.
This time, they replaced the breaker, no problems since. Yes breakers can go bad.
2010 Journey 39n - 2010 Jeep Wrangler - living aboard, touring the extreme 4 corners of the lower 48 this year, started in Blaine WA, east to Maine, south to the Keys, working north through Florida now