I've bought square D breaker that were bad off the shelf also. If its man made it will fail, some just at a higher rate than others.In my book GE breakers are just as bad or worse. When I was doing electrical work we had a electrical fire when a 100 amp breaker didn't trip. We later found all kinds of defective 15 and 20 amp ones.
probly doesn't help that illegal invaders are doing the work americans won't do.I've bought square D breaker that were bad off the shelf also. If its man made it will fail, some just at a higher rate than others.