My Hayward AG 100,000 btu heater ran well for the last two seasons. This season I hear a rattling type noise, and the hose that feeds the heater shakes at times. Other times the noise and shaking subside. The heater is functioning and supplying heat. In The Swim where I purchased it said make sure the heater is level. It was was off by a 1/2 inch and I brought it back to level. It worked initially, but later in the day the heater re fired and the symptoms were back. I just got a call from one of Haywards platinum techs, and he said it sounds like it could be the heat exchanger. He said take the supply hose off, and with a pair of needle nose pliers try to slide the metal plate out of the way as the water could be restricted by the plate causing the noise. Any suggestions as to the symptoms and or advice given by the tech ??