Do you hear an audible click from the high limit thermostat when it cycles the heating element off? If it’s cycling on the high limit thermostat despite having clear and unobstructed venting, it may mean the high limit thermostat is getting on the weak side. Some of the 06 series HOH dryers built from 1966 to 1975 use a L150-20 high limit thermostat, others used a L200-30 (L190-40 will work as well).