Traeger question

Hey ya'll. anyone ever have issues with the LEr code on the Traeger? Mine is an older model that a friend gave to me. ( he is moving to an apt in downtown Charlotte) It's a Texas Elite 34. He hardly used it and kept it dry and covered. I cleaned it throughly but when I smoke ribs, after 2 hours on SMOKE - I turn it up to 275 and it spikes to 400+. and shuts down. I turn it back on and in a few minutes, massive amounts of thick yellow smoke come billowing out and make an explosion sounding noise. I cannot figure out how to get the pellets out of the box -assuming that some may have been in there for a while and have gone bad...... any help is appreciated. Hail State