Had the same problem sort of intermittent problem years ago.
It had bugged the owners of a house for years.
It turned out to be a nail in a floorboard that had gone through a T&E lighting cable and now and again would short out the live and earth.
It had bugged the owners of a house for years.
It turned out to be a nail in a floorboard that had gone through a T&E lighting cable and now and again would short out the live and earth.