American 50 Gal Powerflex

Del

water heater, 6 months in service. HSI ignition with flame sensor, white rodgers gas control.  This unit is intermittently going into lockout with the error code for faulty hot surface ignitor circuit. One of our other techs replaced the gas valve because he could find nothing wrong with the hsi or flame sensor, I did not find anything wrong with it either....I tested room temp resistance, continuity through HSI, continuity through the flame sensor and tested for shorts to ground.  I called tech support, they suggested replacing the HSI/flame sensor assembly which I am going to do tomorrow.  Anyone have any ideas/similar experiences with these P.O.S? We stopped selling these when they had those issues with the gas valves a while back.....must have changed 25 gas valves on the chimney vented standing pilot units all less than 1 y.o.