I have been cycling since 1959 and have witnessed or heard of numerous crank failures. Prior to the alloy cotterless era and way back in the dark ages of steel cottered cranks the makes that regular broke were: British Raleigh RRA and Chater-Lea round pattern, French Durax and Duprat cranks. These were mainly left handed failures. Regarding alloy cotterless sets Campagnolo seen to be the only notable offender. This is probably the reason why British time triallist favored TA or Stronglight sets. I have witnessed numerous Campag failures when I was a starter for our regional time trials. cranks, pedals and titanium bottom bracket axles all failed with alarming regularity. There was even a spate of these Campag failures in the 70's on the professional continental race circuit and several high profile races were lost due to these equipment failures. Last year this subject was being debated in quite a few of the British specialist cycling journals.
Best wishes and be lucky. Michael Butler Huntingdon UK.