Checklists cannot cover ever single malfunction or situation
Flying offshore and the engine instruments of the 76A started signalling by means of semaphore, one engine would run up, the other down in sympathy, then reverse. Identified problem engine,, throttle pulled out of governing range for trip home, then idle for landing. Maintence went with chief pilot for a one hour flight, no fault, put back on line. Bunny has another flight offshore and all was well for 40 minutes. Prior problem engine dropped to zero TQ during a cruise portion, collective dropped to contain good engine, hand was a matter of inches from the problem engine throttle to pull it to idle when it went from zero TQ to max in the blink of an eye. Snapped governor drive shaft. Was when we flew with the overspeeds pulled because of the issues they were causing.