Hello. Long time listener first time caller. My Pentair MasterTemp 250 tries to light off then flames out then enters ignition loclout. Have tried all the usual steps ie cleaned all electrical connections checked all switches and sensors. A trusted associate who maintains heating equipment for a living believes it is a flame sensing issue and after spending an hour with the heater he believes the flame is not being sensed due to something interfering with the flame itself ie some sort of obstruction or distortion in the flame box is causing the ignitor to not sense the flame then the ignition control unit shuts off the gas. Has anyone experienced this or something similar? Thank you in advance and please be kind.