My pool heater turns on, cycles through about 3 times and then turns off and shows “check IGN control” prompt. We had this last year and replaced the entire ignition box. It lasted the rest of the season (IL). This year I replaced the flame sensor rod as I was seeing the glow of flames and thought that was the problem. It worked for about 2 days and then stopped. Began giving the same fault. I believe the burners aren’t lighting all the way. Any thoughts on what to do next?