Chip lights may be spurious, too. The problem comes because you don't know if they're calling "wolf" yet again.
I once diverted three times on one trip due to spurious engine chip warnings. The "fuzz-burn" system didn't make it go away so the engine had to be shut down. I had it checked out each time and it was finally sourced to a faulty plug/harness joint shorting out.
OTH. I've also had one engine chip light that wasn't spurious. The engine mag plug was full of metal flakes.
I've also flown one type of aircraft which had mag plugs but no cockpit warning system. The plugs were pulled by the maintenance crew after so many hours and changed for a new set; then the old plugs were looked at under a microscope by specialists. One morning we landed after hovering at 10,000 feet for most of the night over a city. The main gearbox mag plug had a chunk of metal on it that was too big to come out of the aperture. It was part of a gearwheel and a new main rotor gearbox was needed.