I have experienced the sudden combustion and “explosion” twice on my pellet cookers. Both came as a result of a build up of pellet dust, which caused a bridge on the ramp, then gravity gave way and dumped into the fire pot. It kinda almost snuffed the fire, but the fan kept pumping and finally lit the full firepot. From zero to hot in a second and it does create a pretty good backdraft pop. Lucky it blew out the exhausts and not the doors. But the doors on the FEC cookers are substantial.
As far as the lack of heat question from the OP, I found a solution for my same issue. I build an electric cold/low temp smoker for sausage and snack sticks. I built it out of the Proofing cabinet I got at a restaurant auction. I installed an external Smoke source (bella cold smoker), a 1500 watt electric element designed for a masterbuilt smoker and installed a johnson controls A419 to control the temps. During the summer here in AZ the original element had no problem getting to 185. But heck, I could have got to 185 with a candle in the 115 degree summers. lol Well, as it got colder it got more difficult to reach above 145 degrees. I ordered a finned heat strip and installed on the side of the cabinets. Both elements are controlled by the A419, which just cycles on and off at my set point. I can get about 225 degrees in the winter here with little effort and it even out my temp swings, as it recovers faster. Just an idea