I have installed a Raypak Digital Heater 206k BTU Natural Gas in a commercial facility. The heater display shows the set point at 104 degrees and the heater only heats the water to 99-100 degrees. There are no errors. I left it for a day and the the heater changed course and had a set point of 108 and water temperature of 103 without me touching it. I have changed the board (sent to me by Raypak) and the temperature sensor has been changed. Has anyone run in to this problem and what is the solution.