i have been using rowentas for over 25 years and have never had this problem. because of the high wattage of these irons (usually 1500 watts or above) i keep mine on a power surger strip for protection. there can be power surges in your electrical outlets that can be an underlying problem also.
i now have a 1750 watt rowenta iron and you can believe i have it on a power surge strip, just in case.