My Landrover Discovery Series II has timing belt problems. The teeth on the belts keep getting ripped off – even off a genuine belt. This time the push rods & valves are bent, but there is no damage to the pistons nor any visable damage to the engine. One rocker arm on the rocker shaft is broken. Can anyone shed any light on what might be causing this – it’s the 3rd time its happened in under 1500km!